I doubt we'll see the ecosystems get forced together, though anything is possible.
A shared hardware platform is a different story all together, would make streaming an easier option for both and reduce console R&D. Both could still release a branded console that only played their software, just in a differing skin (auto manufactures do deals like this all the time, especially on the lower profit models). Would likely lower dev costs as well.
That would be a dream. Put an end to this console war bullcrap