I don't think mining is quite dead as a return-on-investment perspective.

I do think you need to wait until the majority of new ASIC hardware has flushed into the stream. Once the majority of that hardware is actually delivered, and people start mining with it, there will be a huge increase in difficulty.

Once that's done though, the influx of new hardware should slow down (or at least no longer come in avalanches).

Then once you see the difficulty increase curve begin to level out (past asymptote), you can begin to make some educated guesses.

But for now, the next major avalanche hasn't even hit yet. So until then, hang tight, or use a few $10 usb erupters for fun. They are still doing 50k satoshi per day.