I have pre-ordered the Canon EOS R. Recently, some lens manufacturers, such as Sigma, have been releasing lenses in the EF mount that have impressive optical performance. Mostly, however, they are trying to get their foot in the door (so to speak) since Canon already has multiple lenses for each of the lens categories (e.g., 24-70 f2.8, 70-200 f2.8, etc.). Now they have an opportunity to "beat Canon to the punch" by releasing RF lenses before Canon has anything on the market in that category. I prefer Canon lenses for their build quality and other factors, but the advantage to us is that Canon undoubtably wants to get their RF lenses out there before the others steal some of the demand. In other words, we should expect a very rapid release of a lot of Canon RF lenses. Of course, it may be the case that Canon has patented the lens mount such that all other lens manufacturers are out of luck for the foreseeable future, in which case my thought is depressing rather than delicious.