Is there an athletic performance clause included in the B1G conference membership bylaws? If not, I view this as a complete non-starter. And even if there is, attempting to boot out a conference member would be risky, and costly.
At this point, the enormous revenues associated with major conference affiliation are going to make it pretty difficult to oust a member of the major P5 conferences, Schools are making their budgets 10-15 years out based on the current revenue numbers as well as conference projections. They're also planning capital expenditures 15-25 years out based on the same.
Any conference that attempted to oust a member for anything other than institutional failure is going to be involved in litigation so fast it will make their heads spin. And if you do it to a state institution, you'll be doing so against state's attorneys.
Which is the main reason I say that in today's financial environment, I believe it to be extremely unlikely.
The B1G added Rutgers for one very specific reason, and for the most part has accomplished its goal. Any athletic underperformance at this point, is simply their cost of doing business.