I've got an R (I love it btw, even without two cards) and I'm really anxious for exactly this lens, or there-abouts. I've got nothing to look through yet because I'm waiting for the polarizing adapter; and none of the first four RFs are a good fit for my needs. Besides this rumored standard zoom I've got a pretty small-niche wish-list, so I'm resigned to waiting awhile. But if Canon is reading this:
A 28mm IS f2.0 Plenty fast but compact, too. No macro required.
A 17mm TS-E that uses filters. Front, back—doesn't matter. 19 or 20mm would be close enough.
A 24mm TS-E compact and with excellent optics.
And yeah, expensive year ahead!