I think the most likely possibility is 10-bit 4:2:2 1080p and 8-bit 4:2:0 4K internal, with 10-bit 4:2:2 4K external recording. 120/1080, LOG, IBIS, and improved noise/DR.
I'd love if they kept the same body design and just improved the guts/display/EVF. It's ergonomically wonderful and that battery has spoiled me for anything else.