Stan: If he is drunk enough he would probably crawl back to wendy, but wouldn't remember it the next.

Kyle: Never ever

Eric: Surprisingly he wouldn't 

Kenny: No

Craig: Maybe, most likely not

tweek: No

Token:  Nah, he wouldn't

Clyde: If he thinks you don't love him anymore or you cheated, he would probably cheat, otherwise no.

Butters: no. who would he even cheat on you with?