I do think that Heaps has/will continue to earn the bulk of reps next spring as well. By that I mean, he should be getting ~50% of the reps and let Nelson, Munns and Lark split the other half. If he continues to keep his PER around 160 the final three games, then he should get more room for error in spring ball, more benefit of the doubt.
If Nelson or Lark or Munns want to unseat him, they'll have to take advantage of every opportunity given, but they'll be given very few. Last year, Nelson benefitted from Heaps not being the presumed starter, so he had time to find his rhythm. If he wants to find his rhythm, he's going to need to do in fewer reps.
Spring ball should a time to further install the offense for Jake, not find a new starter. Now if one of those three is just lights out during the spring in limited reps, then the competition deserves closer scrutiny. But coaches should not use it a wait,wait,wait,wait for a starter to emerge session.
Of course, all of this is predicated on Heaps maintaining his current high level of play these last few games.