Hmm, Very Difficult to say. Some Suggestions say that he might use Izanami, Far fetched? However Sasuke could have received a sealing technique, or just plain Talk No Jutsu. Either way It'll come down to waiting 7 more days.
His jutsu is dying. Really though I'm sure it will be the thing that helps him survive, but I have no idea. I highly doubt it is the rennigan just yet, if ever.
No not rinnegan. That would be lame and predictable.
Kishi is currently taking the manga into a new unpredictable path. So I bet he'll come up with some original shit.