This year is back to a 24 team playoff format. Last year being 16 teams was just for the weird spring season.
Depending on the results of course, but I think 5 teams is realistic. 6 is probably unlikely, though possible (the CAA got 6 teams in 2018 including a 6-4 Elon team and three 7-4 teams). Missouri Valley had 5 teams in 2014, 2015, 2017. Right now we've got (by the STATS poll):
No. 6 Montana St 7-1 (@ EWU, vs Ida, @ Mont)
No. 7 EWU 7-1 (vs MSU, @UCD, @PSU)
No. 9 UCD 7-1 (@ NAU, vs EWU, vs Sac)
No. 11 Montana 6-2 (@ NCU, @ NAU, vs MSU)
No. 15 Sac 6-2 (vs CP, vs PSU, @ UCD)
No. 23 Weber 4-4 (vs. PSU, @SUU, @NCU)
The only upset by one of the other 7 teams this year against one of the 6 ranked teams was Idaho St beating us. Put another way, the 6 ranked teams are a combined 24-6 in the league this year. Take out the H2H games and they're a combined 19-1. So let's assume that continues since there appears to be a clear divide between the top 6 and the bottom 7. That means without any upsets the worst case scenario for each team would be 8-3 MSU, 8-3 EWU, 8-3 UCD, 8-3 Montana, 8-3 Sac, 7-4 Weber. Obviously all the teams couldn't end up at that record since someone has to win each H2H game and there certainly could be an upset or two.
Since the bracket expanded to 24 teams in 2013, every single team that had 3 or fewer losses from the Big Sky, CAA and MVFC has made the playoffs. Some 7-4 teams have missed it but 8-3 = playoffs. So what I'm saying is there's probably going to need to be some upsets for only 4 Big Sky teams to make it.