Unless you're among the conspiracy theory believers who think there was a plan all along to bring in a guy to recruit better than Pelini (not saying that's happened, just that was the plan), who would after 3-4 years step down in favor of Bohl or Frost or whomever.
I can't find any posts where I've talked about this, but I distinctly remember this scenario being thrown around - probably by me

- in the first year-ish of Riley being hired. It was a baffling hire in the first place and, grasping at straws for why he was brought here, that was an idea.
Maybe Frost isn't ready to come here. Maybe the plan was to give Riley one more year and land this group of recruits. Maybe that's all getting tossed out the window with Frost's success and Riley's stumbling.
Maybe this is all some far-fetched fantasy.