Of course, we never know ...
I would have said that we had a two-team Open before it started (Mitty and SMS), but clearly I was wrong. But that said, probably three or four is the right number -- this year.
Next year, both Mitty and SMS will take a step back (though both will still be formidable), and some other teams will step forward, and others back. Much depends on injury, of course, and there are always transfers to consider.
What that means for this discussion is that the Open selections might be even more up for debate next year, because as CityBoy points out, any four of about eight or nine teams could have reasonably been chosen for the bottom half of the Open this year. Next year, there could be 16 teams, say, that wind up in the conversation for all eight spots.
Regardless, any team that gets to a state final, in any division, has done something worth celebrating. Every team left in the final four of each bracket is a good, confident team with some talent, and winning through is an accomplishment.
Sure, SHC could have been in the Open, or Miramonte, or Presentation, or whoever, but all any team can do is play whoever shows up and try to keep winning. And any team that gets to Golden1 has had a great season.