In the last 10 Final Fours, there have been 10 schools that were a 7 seed or lower. Let's recap.
2011: 8- Butler, 11- VCU
2013: 9- Wichita State
2014- 7- UConn, 8- Kentucky
2015- 7- Michigan State
2016- 10- Syracuse
2017- 7- South Carolina
2018- 11- Loyola Chicago
2021- 11- UCLA
That's 25% of the FF teams. Basically, one team a year. 7 seeds are more than likely going to fall out of the top 25. So I'd say a true darkhorse should be someone that isn't currently ranked. I'd be cool if we had 4 top 10 teams in the Final Four. But, here are some teams not currently in the AP top 25 that might have Final Four Potential...
Alabama
Miami
TCU
Mississippi State
Indiana
Davidson