I like that a few of us are thinking a "specialist" TS of some description is in the works. Now we just get to sit and find out if we're looking at a 45, 90 or both redesign.
I like your idea of a 180 L Macro Edwin; my bank account probably wouldn't.
I don't buy the idea of a 100-300, even as a f/2.8 as being a good market for Canon to pounce on. I think its far better to convince people to go for a 70-200 at the stunning and "affordable" price of $2400. I imagine a 100-300 at a f/2.8 would range around the $2800-3200 mark, and would drive people toward the slower 70-300 or the primes. Possibly even the rumoured 200-400mm.
Also noted that everyone seems to believe the 50mm is a candidate for the massively popular lens. I would argue the 50mm f/1.8 is a better candidate than the f/1.4 or f/1.2, but I don't think the price point is a place where Canon can go any lower, unfortunately for those of us that love them. I think the f/1.4 would be the possible offender.
Still, no words on the other primes? I think the primes deserve a good look at for the new versions.