#3 Finn Balor (RAW)
Although WWE is calling this a World Cup, they haven't really told us if superstars in this should belong to various different countries. But I think that will certainly be an element of excitement if they were supposed to do that. Finn Balor is my prediction to fill the next spot for Monday Night RAW.
I think this could be the best thing he could do right now. WWE is clearly not involving him in any title picture and putting him in this cup could have a few advantages. He could provide some really good wrestling matches. If he represents his country of The Republic Of Ireland, he will be one of the foreign participants as well.
I think the Mixed Match Challenge isn't something that does any good to Balor. So it will be a good way of bringing him back to singles competition and restart his push (maybe).