Probably. Or, rather, you can count him as done at the end of the season. I think he can keep his job if he wins the games he's supposed to and avoids nasty thrashings, but even that has probably less than 50% odds right now.
Teams we have left:
Illinois: We should win by at least 1 touchdown.
Wisconsin: We may lose this one; in fact, I'm counting on it. But a victory here in ANY form would be huge for Riley and the team.
Ohio State: The question is simply, how bad do we get beaten? Horribly and Riley's chances get even slimmer. Respectably, and they're fine.
Purdue: We should win this one after having a bye week. I know they're much improved already, but we're far more talented. This one will be bad news depending on the record up to this point. If we're 4 and 3, and lose here, that's not great but we'd live with it. If we have a losing record after losing this game, things aren't going to look great for Riley.
Northwestern and Minnesota: We should win both outings without question, so losing either of these games, again, depending on record, will influence what is going on here a lot.
Penn State: Like Ohio State, the question is how bad do we lose?
Iowa: They're looking like a physical team with a nasty D. Again, how a win or loss here is taken depends a lot on the record at this point.
So, Riley has a tall order ahead of him.
I personally think he needs to keep his job through 2018 barring a complete collapse of the season (which I don't think is likely, but it is alarmingly possible). After that, time for Frosty.