Indoors, I shoot my M135/3.5 at ISO 1600, which is the highest my camera (K200D) has. I use shutter speeds of 1/30" - 1/60", which sometimes results in underexposure (if I had higher ISO I'd use it), but that's the slowest speeds that give a decent chance at a sharp image. Some twill have motion blur, but enough won't that I'm happy. If you visit the "M Club" thread, you'll see tons of examples form me, but here's a small one for this thread:
For situations where 135mm isn't longer enough, I also find f/2.8 isn't often needed, either: the bigger the venue, the brighter the lights, generally speaking. So M200/4 would be worth a look. But I'm talking about getting shutter speeds of 1/60" - 1/90" or so. Good enough for concerts, but for sports, maybe you really would need that f/2.8. I don't know of good cheap options there.