For Scawen's work I'm betting the engine heating (w/broken rads etc) and maybe brake heating.... And of course the tire/aero fixes....
For Eric's work, I'm thinking maybe new cockpits, updated car models for LX/RB4, and maybe a track config since as you pointed out it was mentioned. Since the track config was mentioned so long ago, I think it was already done, but not released yet and he's had more time to work on these other things.
Vic's work is of course the LFS world, who knows what it will be.
edit: I think it's a few things, since in Scawens post he mentioned "some thingS, if the planned things (read: tires/aero) work out well" (paraphrase)