[Tyrannosaurs]

I think you're right that they're likely anticipating this.

Legal cases are like chess - a series of small moves rather than one big bang and it's done.

Lodsys will undoubtedly have hoped that Apple wouldn't involve itself but it would seem unlikely they're going to be put off by a single letter. The very earliest I'd expect them to drop it would be the point at which they got a court summons from Apple or the point at which a settlement was reached (still I'm guessing the most likely outcome).

The next move will likely be an open letter from Lodsys disputing Apple's view and reasserting their claim which will put the ball back in Apple's court but I'd also guess that alongside the public discussions there will likely be private ones going on to which we'll obviously not be privy.