Out of the alternatives to BTC, LTC maybe has the best shot, but that's not saying a whole lot. Once ASICs arrive, I may give LTC mining a go with my GPU rigs and see if it catches on. If enough people do the same, it might actually catch on.
Won't that be too late if you switch at October ?
You won't get as many litecoin if you mine it later, as difficulty keep increasing every few days.
After GPUs users move in, difficulty changed from 1 to 6.6 now.
Imagine the difficulty change in October if most of GPU user move to litecoin.
The total Litecoin network is ~200 MH/s, since scrypt is 1/1000's bitcoin speed, that is equal to 200 GH/s or 0.2 TH/s in bitcoin world.
Total bitcoin network now is 13.3 TH/s.
So roughly only 1.5% hash power move from bitcoin to litecoin now.
Let's say that 30% of 13.3 TH/s is from GPU user, and only 65% will move to litecoin because it's not feasible anymore to mine bitcoin.
30% * 13.3 * 65% = 2.5935 TH/s
After applying 1/1000 multiplier, that's equal to 2.5935 GH/s
Current litecoin network is 0.2 GH/s
If the network speed grows from 0.2 to 2.7 GH/s, the difficulty won't be 6 anymore and less coin will be generated per kH/s.