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Cruise's career has nothing to do with any other factor than this.
How much box-office do his movies do?
Period.
Right now he is hot again off the worldwide revenues of the latest Mission Impossible blockbuster.
If he starts to bomb regularly, the movies roles won't dry up--just the budgets and he will appear in more modestly budgeted studio films, not commanding his $20M salary and huge profit participation.
If those films tank, he will be relegated to independent films (financed outside the studio) and there is nothing preventing him find finding vehicles that are appropriate for his talent and personna--being surrounded by an outstanding ensemble and helmed by a world-class director.
Hollywood doesn't care about anything other than box-office success and, failing that, secondarily, critical acclaim (i.e. Academy Awards, Golden Globe awards, etc). By way of example, Woody Allen has made films with great regularity which almost never are a box-office winner. His art is driven by words, performances, cinematography and other craft that are not even trying to compete with major studio releases.
If all else fails, there is a starring role in a TV show. It is one of the well-established paths for actors past their prime.
The only other path that has been blazed is politics, but unless Cruise is trying to become mayor of Clearwater or Hemet, there is zero chance that he will not be laughed off the ballot. And he wouldn't even fare well in a tiny, Scientology-controlled venue like CW or Hemet either, so let's just rule the Ronald Reagan Routing Form out.
There is an outside chance that Cruise decides to try his hand at directing, like Clint Eastwood, but no evidence exists yet that he has the talent or vision to do that.
My guess is that his career follows the same trajectory it has been on for quite some time--downward.
Unless he publicly leaves the cult. Then he can go back on Oprah and do a contact assist on those couches.