It won't replace the 70-200LII but it'd give a nice alternative to shooters who don't need the size and weight and need some extra speed.I've been raving for the 135L for awhile now but it seems to get washed out by the "eermegerd 85mm 1.2!" Consistently... :/
It's a near perfect lens and it deserves a makeover with a bump in aperture and IS. That will make it a lens that I'd have absolutely no reason to own a 70-200II. Dedicated portrait photographers would flock to that prime instead of spending the weight and monies on the 70-200II.
I just love the 135L. It's the reason I like primes over zooms. Light, small, fast and affordable.
Since I don't do photography for living, I can live without 135L. The 70-200 f2.8 IS II is a MUST have lens for my shooting.
There is nothing much to complaint about current 135L, except lacking IS for those 1/60 or slower shots.
I've been thinking about 35mm to go with 135L for low light. The love for 50mm focal lenght has changed to 35mm now.