We saw the Pilotwings artwork and the retail listing for Rogue Squadron was leaked.
We know that they were working on 2 games for Nintendo and that those are the only games they supposedly moved to the new studio since everything else was being funded by Brash Ent. and that company sinkholed.
I've linked and sourced everything in the Rumor thread, feel free to browse it.
I'm not saying it's 100% confirmed, but where there is smoke, there is usually fire, and Factor 5 had a lot of smoke, backed up with retail leaks and dev artwork.