I think there are so many uncertainties at the moment that its going to be tough to call. A lot depends on Ogier and his decision. He will have made his mind up before Spain in October and that decision depends on Ford coming back as a manufacturer. If they do, he will stay, if they don't then he will be at Citroen. If he does go that leaves at least one seat open and M-sport, I am expecting Tanak to also leave and go to Toyota should Ford not commit to the WRC. Mikkelsen could still find himself without a drive should Ogier go to Citroen, I believe Citroen see him as a plan B to getting Ogier. That would leave options for Mikkelsen at M-sport but after testing the I20 earlier in the year, I would think he would be more likely to end up at Hyundai should he not sign with Citroen. Below are my guesses at 2018

Ford
Ogier
Tanak
Evans

Citroen
Mikkelsen
Meeke
Breen

Toyota
Latvala
Lappi
Haninnen

Hyundai

Neuville
Paddon
Sordo

Or

M-sport
Evans
Camili
Suninen

Citroen
Ogier
Meeke
Breen

Hyundai
Neuville
Mikkelsen
Paddon/Sordo

Toyota
Latvala
Tanak
Lappi