Look at it this way, will you have to worry about FPGA or ASIC vastly decreasing your profitability in the future?
That's not the only factor, the way I look at it is everyone going to continue to have interest in litecoin? What if it drops along with bitcoin(it will, no doubt about it), then what? Sell of the ole GPU's and buy into asics when the wait lists are over? Time and time again, it's the same old story for mining, at least every second person is trying to strike it rich or make money off of mining. This IS the electronic american dream.