Gotta say, Jeff/Annie all the way.
While I enjoy the bickering sibling vibe between Jeff and Britta, there's kind of a mean-spirited edge to it that I can't get behind. And this from someone who would normally be rooting for Jeff/Britta. The truth is, I disliked it even back in season one back when I shipped absolutely nobody. I didn't even start shipping Jeff and Annie until season three, so it's not at all about Jeff/Britta being a rival ship.
Also, I'm curious why you believe this:
Because going by all the episodes that came after VSA, it's pretty obvious that Jeff/Annie was never sunk and that Annie was outright lying to Abed. In fact, Dan Harmon has famously said that he never left Jeff/Annie as a potential for a romantic pairing.
Annie's continued to flirt withJeff, and she was devastated in the final epiosde of season five when it looked like Jeff and Britta were getting married. So, while it wasn't clear at the time VSA aired, everything Annie has said and done since then with respect to Jeff pretty much spells out that she wasn't telling the truth. This was capped in the final episode of season five when, in her Winger speech which was a thinly disguised speech about her feelings for Jeff, was that no matter how much she cared about him, she was willing to accept that Jeff didn't want her in return and that he should pursue whatever it is he actually wants.
Plus, from Jeff's end we know he has feelings for Annie. At the end of S4, he had an elaborate fantasy where Annie wasn't just his partner in crime, but also his sexual partner and apparently in a monogamous relationship with her. At the end of S5, we had confirmation that Jeff felt something a whole lot more for Annie than just mere "friendship," when thinking about her was enough for him to reboot the school computer. (It was confirmed by the writer of the episode on Twitter that it was Annie, not the group, that allowed Jeff to reboot the computer and allow them to escape.)
So, yeah. It actually wouldn't be forced if they went ahead with Jeff/Annie in season six because they've been building up that pairing all along. Now is it likely it'll happen? Probably not. Dan Harmon likes writing the tease, but there's no way he's going to go through with the execution.
Plus, Dan Harmon and Gillian Jacobs pretty much confirmed at ComicCon that Jeff and Britta are over and done.