It's not gonna be some big major swerve that nobody would see coming in a million years, i.e. The Rock, Hogan, Austin etc. Cause if WWE had gotten one of those huge names to make a one time appearance, it wouldn't be on Raw in the middle of May.
So it's gotta be someone who's returning. It can't be Triple H, he hasn't been gone long enough for the hypocrites complainers to go "We need Triple H back to save the show!"
So I think it's between HBK and Kennedy. HBK has had enough time off, it would boost ratings, people would pop for him like crazy and he's be able to have a face off with Flair over Flair's possible return to the ring, which we all wanna see.
If Kennedy was the fifth member, that would mean making him return in a Raw main event, which would mean he's being pushed as soon as he returns. While I personally would like to see that, I don't believe WWE would push him so early from returning, they need to make sure he can stay healthy for 6-12 months.
People are suggesting Flair, but meh. I mean, he's already been around for the last couple of weeks so technically, it wouldn't be a surprise would it? Maybe it's just me.
But either way, they'll be dropping hints on Raw all night before the main event starts. So I'm guessing we'll know who it is 15 minutes into the show!