On the Gear VR (dev kit, 2014) there was a 2.5k screen at a smooth 60fps. The consumer Gear VR coming out this fall will likely have a 2.5k screen but we'll likely see 4k screens on mobile headsets in 2016. 120fps will be a nice improvement but not required, with the Rift CV1 at 90fps and sufficient for presence. So we're talking a 2-4x difference.

The graphics card issue is not that relevant, Gear VR with a mobile GPU is showing that it's not really about some arbitrary graphical fidelity bar. Yes, some of the highest fidelity cool stuff will be on PC but multiple cards won't be required. Both the Vive and CV1 will run great on one high end card, and by the time they upgrade to ~4k/120Hz... they'll still require just 1 card.