Thats exactly why I'm trying to combat all that blather! Don't listen to it...it has no bearing whatsoever on the cameras ability to take excellent photos...its just a bunch of tech heads who like to tear apart hardware and data at a low level and find its flaws (or lack thereof, if that tickles their fancy.)
Its all meaningless in the grand scheme of things! Learn how to use your camera, use it effectively and efficiently, and those issues will only affect a very small percentage of your total photos. If you need real evidence of whether any one of the cameras on the market today, including the 5D II and by extrapolation the 5D III, just look for photos created by them on sites like 500px.com or 1x.com. You'll never see any banding, fixed pattern noise, or DR issues.
It is meaningless blather for SOME but not for others. It depends how you shoot, what you want to shoot. I can hit upon the limit often enough that it's annoying, in the REAL WORLD. It's meaningless in the grand scheme for some but not at all for others.
If you plan to shoot 99% at ISO800+ then it is probably 99.99% meaningless.
For some they may run into the issue routinely though, although sure you can still take tons of great pics if you avoid lots of stuff you wanted to do or wanted to do without hours of post.
And by constantly saying it's just ridiculous nonsense by tech-heads (was Ansel Adams a tech head? well haha actually he was but you then doubly get the point) all you do it make those mentioned the stuff mention it more to add some balance to all the head in the sand, maybe that ends up having us make it seem like a bigger deal than it is.
The grand total difference from the worst current Canon body, the 7D, and the best current Nikon body, the D7000, is less than a full stop. The difference is even less, from the 1D IV to the D7000, of about half a stop. In terms of more realistic, real-world shooting...you shouldn't concern yourself with the low-level nature of read noise and how it may affect the technical specification of DR.
Those numbers are not more real-world, they are nonsense and you who makes such a big deal about getting the exact truth well knows that. They way understand the differences when they even have any semblance to reality at all for the RAW shooter in particular.
That said the OP shouldn't just go crazy and do something without examining what their needs, it could at least as easily be that it would mean little to them as a lot, and even if it proves they would benefit a lot from more base DR it might not hurt to see how the 1DX does, if it does much better then maybe the 5D4 will finally do much better and it's then a question can you wait another 2-2.5 years, that can be easier than switching, it depends.
If most of you wedding shots are at ISO800 and up I don't think it would make sense to switch and for wedding shots that you are doing and portraits in what you are doing 22MP is fine and SNR and DR may be no different from mid-iso and up, the new 5D3 AF may be more sensitive in dim light (but you really need to wait for user reports) too. If you did lots of ISO100-200 shots and were often struggling with black tuxes and white shirts and huge DR and couldn't hide it well enough then maybe, but I imagine with use of fill flash and a little hiding in post you can get away with it for your new portrait and wedding business, for portraits you can really have control of all lighting and making use of radical DR shots or not I doubt will make or break you (but losing money switching around might). For portraits you could probably fast shoot two shots for HDR anyway, portaits can be so controlled and I doubt you are doing the sort with a constantly moving model doing this and this but probably purely static, rigid stuff.
That said some people, real world, make great use of D800 DR, I sure wish the 5D3 had the extra DR myself. For you I just have a weird feeling you might just lose money and get annoyed from teh whole swithcing process, at least now.