They've said up front that the System Shock series is not part of their deal (which makes sense, as SS2 is the most wished-for game on GOG by some margin). That's a bummer. But there are going to be a lot of stone-cold classics coming down the pipeline. I still maintain that Alpha Centauri is the best thing Sid Meier has ever done and I'm greatly looking forward to freezing some motherfuckers solid in Crusader. Every game they've announced so far is awesome.
The announcement also stated that after the currently listed games are released, there would be a lull in the schedule, so heads up.