That said, I would still love to see an updated 35mm f/2 with USM, and perhaps a high quality 50mm f/1.8 or f/2 with USM.Well, the 50mm f/1.4 has USM, so that would fit your needs in regards to "high quality 50mm", and the price is within this realm (usually <$400). Aside from adding IS, Canon doesnt seem eager to update their non-L primes, so, I wouldn't expect too much. But, an EF mount mirrorless would mean they might start updating primes more, and that'd trickle down to the DSLR side too.
40mm on a 2x crop would be 80mm... I'm not expecting the mirrorless to be anything more than APS-C, it is just as likely to be the same size as a 4/3rds sensor, EF-M ? (micro) in a way of beating Nikon on sensor size (Nikon 1), but not suffering a problem of having to build masses of new lenses, as it would be EF or EF-S comparable.I was thinking the same thing originally. This would be the portrait lens, and then they'd have a few other pancakes and a 14-42 and 14-100+ zoom that would come out eventually too. But, that there haven't been any rumors, and I don't really remember patents for them, so who knows
So, could we also expect a cheap 12mm and 24mm pancake too ?, giving 24mm and 48mm focal lengths ?