The surprise for scrypt miners will come when mining scrypt is not profitable either. Who would trade ASIC earned BTC for GPU earned LTC at an effective loss? Yes I do believe the LTC economy is just an accessory to the BTC economy and can't stand up on its own right.
I agree, and then difficulty will drop until enough people are making a profit, somewhere someone will be mining scrypt profitable but unless you have cheap power and are prepared to optimize your rigs for efficiency I wouldn't bother. Worst case scenario scrypt mining in 6 months consists of people with free power looking for pennies on the bottom of a very deep well, but I doubt it will get that bad.
The thing LTC has going for it is when/if mtgox finally implements trading and fuel another bubble for a few weeks/months, long term I don't see even that saving profitable scrypt mining for most people however.