Based on all the infos it seems that those new 50 / 60 Ghash will behave like 2 ghash right now, so if the price keeps rising it's a good investment even if you receive it in 2 or 3 months
Agreed. The market will find a balance. The ASICs of the world will eventually balance each other out and their ROI will fall greatly. Only those who get theirs early will find a nice profit before the BTC difficulty gets too high..
When ASIC are widespread GPUs will be like CPUs are today (not worth mining).. But the price for ASICs will drop dramatically as their ROI shrinks and we will be buying them like people buy GPUs today. (It will not make sense to pay 20K for a 50GH/s miner)
BTC value may speed or slow things up (as it affect ROI), but the ever-improving technology side of mining is inevitable.
The only question that remains is the timetable for all for this to unfold. Avalons are not shipping in great numbers. BFL has still not shipped and many think they never will. BTC value is slowly growing since the last bubble burst. So, IMHO, GPU mining (and FPGA) will still be profitable for a little while longer at least.