It doesn't make the slightest bit of sense for there to be any internal "debate" over which mounts to make it for. Lenses aren't mulled over for years then quickly slapped together at the last moment; if the lens was going to come out in 18 months, let alone 12, that would mean prototypes are already made and the optical formula, in particular, would already be mostly in place.
Which means if there is any question over the mount then the optics can't be optimised for the R system; what you're suggesting is they do like Sigma and simply build in the basic adapter onto the EF version of the lens. Considering they are selling four adapters (three w/ two SKUs for the filter adapter), and the whole selling point of the R system being the new lens mount allowing for better designs, it makes no sense at all for Canon to develop an EF lens then build an RF adapter into it. Either they're going to design the lens for the R from the ground up, which means an optical formula which won't work properly on EF mount, or they'd make just the EF version and have people buy the existing EF-RF adapters.
If you posted this report verbatim, then whoever your sources are don't know how lenses—or any technology product, really—are developed. If you paraphrased them and wrote the copy yourself then either they don't know how these things work
and/or you misunderstood what they were saying. Either way, neither of you thought through the logic of these statements.
I'll reiterate, if the lens is supposed to be on store shelves in 18 months then that means they started designing it at least one year ago—if not two years, and potentially many more—and usable prototypes are currently out there. The last 3-4 months of a lens' development are spent entirely on marketing and getting units produced ready to be shipped out for release, and the year before that is spent testing the design and making incremental tweaks. If it's 18 months away from being in public hands then its mount and the majority of the optical formula and electronics would have been laid out sometime in 2017 or earlier.
You don't spend 2-4 years coming up with a lens then right at the start of UAT start questioning whether you've put the right mount on it or not.
Hard to believe there is a debate. Not sure how R sales are going but they didn't seem to be flying off the shelves. Very little chatter on the pre-order threads, stores have them in stock the same day pre-orders start shipping and CPW had street price discounts day 1.
FWIW, here in the UK it's selling at around the same pace as the 6DmkII, 7DmkII, D500, and the average Fuji body, according to the staff of the local branch of the main UK photographic chain store. (Who generally know what they're on about.) I.E. it's not breaking any new ground but it's doing "fine". Which is about what I'd expect given that, even though new lens mounts are what have always changed the photographic industry in the past, these days everybody is just focused on which sensor can eek out another .5 stop of DR.
Right now I'm buying my life kit, I won't be buying again unless something fails. If Canon were the only game in town maybe a lens could swing me to R but 3rd parties are already at the plate with top notch EF mount lenses so there is no need to wait on Canon or let them push you in any direction. It's a shame Canon didn't release the IS along side the current 2.8, rumors have it they had prototypes in the field. They would have had my money years ago.
As it happens, I'm in a similar position but looking at the R specifically
because of the lenses it offers. I'm hoping to change up my work in the new year so I won't have such high demands on gear and can go more with what I'm comfortable with rather than what fits the technical requirements; I hope to get everything done with one system and I hope to not have to update that system. Getting the next ten years done with one bag's worth of kit is my goal. "Life kit" may be stretching it, but long-term, certainly.
And to that end, the 28-70 f/2 can get a helluva lot done in just one lens, and nobody else has anything like it nor even rumoured to be working on such a lens. If that lens didn't exist or if other companies had equivalents out or upcoming, I wouldn't look twice at the R; I'd just expand my Fuji gear and buy a couple of X-H2s when that body comes out. But the RF 28-70 f/2 is keeping the R on my radar. If Canon can hurry up with a more pro-grade body (two cards, IBIS, better battery life, further sealing) in the next year then I'll go all-in on the R and that f/2 zoom.
