So anyway, is this camera going to have sensor image stabilization when it finally comes out, or what?
Probably not.
+1
After all, even the first Sony (and Fuji) Ml didn't have IBIS. I took them 2 or 3 generations (or several more, if your count from the ancient NEX family) to implement it.
BTW, if the future 5DM had IBIS, how could Canon sell us the 5DM Mark II in 202x?