Yes. In practice you'll end up with a 77 mm filter.135 divided by 2 is only 67.5mm, with the barrel thickness, they end up with 72mm filter size
Canon's 135/2 has a filter size of 72 mm. Same as the 200/2.8
135 divided by 1.8 is already 75mm of opening, + barrel thickness, i don't think 77mm (+2mm) can do, thats diameter, not radius
It probably could
, the barrel is not thicker than 1 mm (so 2 mm added to the diameter). But it depends more on the optical design of the lens - my guess is that a larger diameter front element will be used to reduce vignetting, and an 82mm filter will be the result. More lenses are coming with 82mm filters these days (Canon 16-35mm II, which I'll point out increased in diameter from the 77mm filter used on the MkI version of that lens), the TS-E 24mm II (and the MkI version of that lens used only a 72mm filter!).
In that regard, I really hope B+W comes out with an 82mm ND 3.0 (10-stops) - well, I've been told that they will not, but their parent company, Schneider Optics, might...