History as in the last ten years says three. . .
With the giant caveat of . . .
. . . RPI is weighed so heavily.
. . . this.
2013 - Second place OSU (RPI #53) and Third place Nebraska (RPI #46) left out. 5th place Illinois (RPI #44) gets in. Two teams total.
2014 - Third place Illinois (RPI #56) left out. Two teams total.
2015 - B1G gets 5 teams. The 4 at-large teams had RPIs of 13, 29, 34 and 42.
2016 - B1G gets 3 teams. The 2 at-large teams had RPIs of 50 and 53 but finished first and second place in the conference. Michigan had an RPI of 39 (5th place) - left out. Illinois had an RPI of 55 (6th place) - left out.
2017 - B1G gets 5 teams. The 4 at-large teams had RPIs of 34, 40, 44 and 54. The team with RPI of 54 finished in first place in the conference. Minnesota in 4th place with RPI of 72 left out.
2018 - B1G gets 4 teams. The 3 at-large teams had RPIs of 34, 40 and 46. 7th place OSU gets in with a 46 RPI and 4th place Illinois left out with a RPI of 50.
2019 - B1G gets 5 teams. The 4 at-large teams had RPIs of 35, 38 and 40.
2020 - COVID cancellation.
2021 - COVID restricted play. 3 teams. 2 at-large teams have RPIs of 56 (Maryland) and 94 (Michigan). Numbers skewed because of conference only play.
From 2013 - 3rd place finishes:
2013 - 3rd place (RPI 46) - left out.
2014 - 3rd place (RPI 56) - left out.
2015 - 3rd place (RPI 42) - invited
2016 - 3rd place - automatic qualifier
2017 - 3rd place (RPI 72) - left out
2018 - 3rd place (RPI 63) - left out
2019 - 3rd place (RPI 38) - invited
2021 - 3rd place (RPI 94) - invited
From 2013 - Highest RPI from B1G invited to tournament as an at-large
2013 - #53 - Second place in regular season
2014 - #33 - Second place in regular season
2015 - #42 - Third place in regular season
2016 - #53 - Second place in regular season
2017 - #54 - First place in regular season
2018 - #46 - Seventh place in regular season
2019 - #40 - Fourth place in regular season
2021 - #94 - Third place in regular season
If you set aside the '21 COVID anamoly, there hasn't been a B1G team that has received an at-large berth with a RPI higher than #54. The only at-large invitations to teams with RPIs greater than 50 (3 times) have finished the regular season in either first place or second place (twice). The highest RPI of a third place finisher to receive an invite is #42.
By my review of the numbers, history suggests that there is an excellent chance of getting an at-large invitation if you finish with an RPI in the 40s OR if you finish first or second in the conference in the regular season and have an RPI below 55.
Other than the '21 COVID anomaly, since 2013, there is no historical precedent where a B1G team with a RPI in the 60s gets an at-large invitation, let alone precedent suggesting that a third place team with an RPI in the 60s receives an invitation.
The numbers don't lie. If Iowa finishes in 3rd place with an RPI in high 50s or low 60s, receiving an at-large bid would be a deviation from what has occurred since 2013 (again, excluding the weirdness of last year).
Don't get me wrong. I don't like it. In fact, I hate it. But, that's the history.