I'd wait for the M4. It's going to be amazing.

I'm struggling with the same thing. I'm thinking of just pulling the trigger on the E92 M3, drive it for a year or two, and then sell it for the M3/M4 when it comes out...best of both worlds!

I'd wait, first turbo M-car, so it will be special for sure. The only thing I'm worried about is turbo lag, and issues from a direct injection engine.

Wait, worst case I'm sure you'll be able to find a practically new M3.

If the twin turbo 335i had 300tq at 1500 rpms....I'm sure there will not need to be any worry about lag.

I have two 335i, and it's very noticeable... Not like an STI or EVO, but no matter what turbos don't spool instantly, closest is something like the variable system in the newer Porsche Turbo.
Figures don't tell the whole story, I can't wait to drive the M4. I'm sure it will be much better than the N54/N55 engine in the 335i.

Ever since I drove an e92 M3 for a week straight, I can't stop thinking how unresponsive the 335i engine is compared to the M3's V8 instant response.