I welcome the day when E.V.F. equals then surpasses our mirrors & prisms. There are some huge advantages to e.v.f. . We are getting closer but not quite there yet. When it equals & surpasses what we have presently - great & good but until then no thank you.
Better yet just let me wi-fi stream everything to my contact lens overlays and I'll be as happy as a pig in §π¡±.
Generally speaking, an optical view finder (OVF) will always be superior to an EVF in certain ways. For one there is little to no limit on the amount of detail or amount of light you could observe through an OVF. EVF's, being small digital screens, will always have certain limitations...on dynamic range, on resolution, on response time. Their small size is both a benefit (allowing the use of super cutting edge screen technology that costs a lot without it costing too much) while concurrently being a detriment (you can only do so much with so little space). We don't notice the limitations of a beautiful AMOLED screen on our smart phones because we observe them from an average distance of 10 inches...however when the same kind of screen is a mere inch or two from your eye, its limitations and flaws will become readily apparent. The key limitation that I think will always prevent EVF's from "surpassing", and possibly even equaling, an optical prism-based viewfinder, is dynamic range. With an OVF the only limit is your eye (i.e. you couldn't and shouldn't look at the sun through a camera)...however you could look at a very bright sky, and still pick out detail in the shadows with a little bit of focus. An EVF, even one using technology years from now, will never be able to offer that much dynamic range...something will have to give. You'll either get blown highlights, or lack the ability to see detail in the shadows.
There are also the inherent lifespan problems with an electronic screen...OLED devices use organic substances that have limited lifetimes. Even inorganic technology can burn out, either at the pixel level (leaving you with a dead or stuck pixel or pixels) or simply dying entirely. How many times have you heard anyone say they couldn't use that 50, 70, 80 year old or even older camera because the view finder was burnt out? Never. An optical device will last forever, so long as it doesn't receive enough shock to break it.
I think the DSLR could be improved in one primary way. Since they use electronic sensors, I don't fully understand the need for a shutter. If we drop the shutter from DSLR's, that leaves only the mirror itself as the last mechanical component that could possibly wear out from extended use or age...and they are (and have always been) easy to replace if necessary. An electronic shutter could open up new avenues for DSLR's as well.
I find the newest EVF's to be really good and I wouldn't mind using one. I can already see the composition really well and I don't think you need to see insane amount of detail and DR through your viewfinder. EVF's can provide more information like a histogram and a electronic level. Also in low light condition evf's are much brighter.
Camera's can't last forever anyways. Because of mechanical wear, camera's are rated a limited amount of clicks , for example 150 000. An EVF can actually limit the amount of mechanical wear. OLED's last about 14000 hours. Assuming you look a minute (which I think is really long) trough the viewfinder for each shot, the evf will last you 840 000 clicks.
Optical viewfinders these days, at least from Canon, already include a high resolution transmissive LCD screen. You could easily add a histogram or electronic level overlay, as well as pretty much anything else, to such a HUD. A dynamic viewfinder with useful information is not relegated to the realm of EVF's.
As for mechanical wear, read my second paragraph...I concur that a mechanical shutter is the only real legacy hangers-on in DSLR cameras, and it could easily be dropped...but keep the mirror and OVF. As for EVF lifetime...the EVF is always on if your actively using the camera as far as I've seen. Were not talking about an electronic shutter when referring to an EVF (and an electronic shutter could be used on DSLR cameras in place of a mechanical shutter as I already stated.) An Electronic View Finder, if your actively using a camera for hours at a time, will be on and wearing the whole time. I often spend 8, 10, 12 hours a day (when there is enough light) with my 7D out in the field photographing birds. I recently spent nearly two solid weeks out every day from morning till sunset photographing birds. I'm looking through the viewfinder for most of that time. If we assume I spend 8-9 hours a day looking through the viewfinder, thats about 4 years of OLED life. Once it dies, your on the hook to get it fixed...which means finding and hitting up a repair shot, leaving your camera there for however long it takes to replace...and, on top of it all, paying to replace a wearable part. Depending on usage, that might be longer than a shutter...but its a hell of a lot shorter than the overall lifetime of a heavily used camera body could take, and a hell of a lot less time than an OVF would last. With a 1D X, I could keep the same body, with the same shutter, at the rate I take photos for over 4 years, and keep on going. If I had an EVF, an OLED viewfinder could die well before that.
The hype around mirrorless cameras is, IMO, rather unfounded. There might come a time, years down the road, where we find a way to produce mirrorless cameras with EVF's and electronic shutters that provide functionality that surpasses DSLR's enough to warrant such hype...but that is years, maybe even decades, down the road. Today, next year, over the next few years...I feel there is very little to be so hyped up about in regards to mirrorless, particularly as a DSLR killer. There are so many things still going for DSLR's that put current and prospective mirrorless cameras to shame.
Note that the EVF is only on when put your eye on it and shuts off automatically when you don't. But if you look 8 hours a day trough a viewfinder I guess EVF's are not the right choice for your application. For most people, the camera will die way before the viewfinder burns out.
I don't believe the hype is unfounded. Most of the hype come from pros and enthusiasts who already have DSLR's. Mirrorless camera's can provide a compact, lightweight and yet high quality solution which many people fancy. It might not be the best option for something like bird photography, but bird photography requires really big tele lenses, which defeats the whole purpose of compactness anyway.