It is a tough decision to make. If I am the AD, I give Helfrich another year. I want to hear him explain what went wrong this year and what they are planning to do to fix it. If his responses seem on track, I give him another year with an expectation of what is needed to maintain the job beyond next year.
I'm not the AD, so let's assume he does decide to let him go. I can't imagine they go to Frost. They basically already tried the elevate an assistant to head coach and that didn't pan out. While Frost had a nice year at UCF, I don't think that is any guarantee that anything different would happen at Oregon. I imagine they'd love to have Chip back on the sidelines and while I think Chip really wants to be successful in the NFL, he may grow tired of the lack of success he's had. Granted, I don't think Belicheck would have had better success at SF based on the talent they had coming back.
I think there's a lack of home run hires out there right now, sans maybe the guy at Western Michigan - but that is taking a bit of a shot. I guess maybe some team may try to poach the Colorado coach after their pretty remarkable turnaround. I don't think Les Miles would fit the Oregon culture, in my opinion.