This was very predictable (from September):
https://bitcointalksearch.org/topic/m.1200541
(just bought an additionally 7970)
What do you expect? 10K odd GPU mofos selling every LTC they mine for BTC. That's a downward pressure. If a number of them decide to hoard, that's an upward pressure. But as a general rule, short-term minded miners who would be expected to flock to LTC are likely to bring the price down. LTC are simply not traded almost anywhere and they don't offer any big advantages over BTC. Basically the core of LTC who just wanted a GPU free environment will see that goal definitively destroyed.
GPU have very little future as mining equipment. The whole project would be pointless now with a GPU-dominated ecosystem and no single meaningful advantage over the coin that has all the traction - except for those with large quantities of LTC.
Anyone could have predicted the demise of LTC -- it's just the latest "me too" blockchain that has NO advantages over Bitcoin. At least not when all advantages/disadvantages are totaled up and weighed.
Bitcoin has an order of magnitude more traction, acceptance, infrastructure than all those alt-blockchains put together.
I'm sure LTC won't be the last, either.