Looking back through recent history... these teams all missed out on the dance.
St. Mary's (2015-2016) - 26-5, 38 RPI, 148 SOS
St. Bonaventure (2015-2016) - 22-8, 30 RPI, 81 SOS
Colorado State (2014-2015) - 26-6, 29 RPI, 111 SOS
Southern Miss (2013-2014) - 25-6, 34 RPI, 132 SOS
Why cherry pick these teams? They've all got decent RPI's with bad SOS's. Good win totals (except for St. Bonaventure, but they had a better SOS), and none got in. There's at least 1 example of this a year.
According to RPIforecast, ISU currently has a projection of 36.3 RPI, 123 SOS. That would lump them in this group without any good wins on the resume.
If ISU runs the table? Projected at 27-5, 23 RPI, 111 SOS. Better RPI than the above, but the same general grouping. Still, no good wins on the resume. Missouri State carries the torch with a 21 RPI to not get in... ISU just needs to continue to play well and focus on St. Louis. That's the best hope any Valley team has right now.