From what Fujino said, one ending will be Kirito turning into a cuck. To be fair, the story has changed drastically since then, but the cuck ending is still on the table, and I'd say with the new hallucinations, now more than ever. So maybe there will be more endings than the two Fujino originally aimed for, but one of them will certainly be a cuck happy ending for him.
As for the cheating, well, since his corruption meter is near 50% now, he's already pretty open to not being absolutely faithful. As we saw in the last Sinon scene, he didn’t really hesitate to help her out. I think once he reaches like 60-70%, he'd probably be okay to go all the way, even if feeling uncomfortable about it. Logically, by the end of the game, he wouldn't mind at all, I guess. Which will also include him being okay with Asuna cheating.