The impression I got from something the female presenter said on Thurs' Xtra Factor was that only one act was going home, so that part seems true at least.

Cheryl just tweeted after 10 mins of voting tonight someone is leaving after the end of tonight's show

That would explain why Ed Sheeran is performing on tonight's show, annoying though as I won't be watching live, so won't be able to vote during that 10 mins

They did a couple of doubles this way last year

so the OP is right after all