As far as in next few months ASIC's hit the market it is the question of time, probably few months, for difficulty of btc to go high enough, so all non-asic miners will stop mining, the only alternative, as I see it, the litecoin (is the only another promising alt coin) which will allow them to continue mining.
Current ratio litecoins to bitcoin is about 1:44
So, what we might see next, litecoin market will start getting new miners who is switching from btc with their GPU boards... which is good for litecoin, more people, more trading the litecoin price might go up in first, that means that all these people could buy btc simply by trading their ltc for btc, this is what I think will happen in the beginning, ltc will rise, on other hand btc market will have less traders, which could push down btc even more and make ltc/btc ratio even more smaller, but after that, as far as of now most people and investors(venture capital etc) believe that only bitcoin is the only real internet currency, all those thousand of new ltc miners that join ltc after dumping btc, will start to trade their ltc to btc, which will push btc high, taking in account that suddenly there will be a lot of people trading their ltc for btc, btc price will rise much higher then current level...
Community needs somehow to add value to LTC , I see BTC rise in value as of Butterfly/AVALON accepting only BTC so people had to trade USD/EUR for BTC thus lowering availability of BTC.
I don't see why should anybody trade fiat for LTC. This is IMHO I am not an economist but you need somehow to add a value to the coin, mining it wont rise it much and trading it for BTC would just drop the price, so GPU guys may even stick with BTC untill profitability is -0.01 than sell GPUs and buy ASIC as there will be lot of ASIC on a market to buy by the end of the year. Of course I may be completely wrong I am still a newbie