As a true confession, the addition of Nebraska to the conference in 2010 was finally what got me really into college sports, and football in particular; before I was just a casual fan, but the machinations of expansion just got me hooked. Anyway, like many of you, I was fairly disappointed by the recent move to pick up Maryland and Rutgers, and don't really see it ending well. At any rate, after spending way too much time thinking about this, I think expansion has died off for the forseeable future, though not for the reasons I have seen elsewhere (ACC grant of rights, etc.)
It seems to me that every conference has a "utility" that it wants to maximixe, and will add schools accordingly. The SEC wants to maximize football success, so A&M was a good choice, even if they thought it was largely a move to pick up Texas recruiting at the time. The ACC wants to maximize basketball success, which is really the main reason to pick up Pitt and Syracuse. Our precious B1G wants to maximize money, and to a lesser extent power (if it wanted to maximize power purely, it would go the SEC route of picking up football schools, and focus less on academics). Nebraska was to get a historic football brand which was available, and Rutgers and Maryland were demographic cashgrabs, which were likely shortsighted.
So, given all that, why is expansion dead for now, at least for the B1G? Well, in the interest of being provocative, the best way to put my point is that there are actually too many schools left to choose from to make any of them practical. A rule I have seen with expansion so far is that schools central to the existence of a conference do not leave for other conferences (Nebraska was not the be all end all of the Big 12 like UT or OU are, Maryland was expendable to the ACC in a way that UNC and Duke are not, etc.) For the purposes of this comparison, the most comparable conference to the B1G in terms of its goals is probably the PAC-12. If you recall, when the PAC-12 tried to expand last time, it went with the Texas and Oklahoma schools at first, and was willing to take all of them to get UT and OU. That fell through, so it was left with the Rutgers and Maryland-like demographic grabs of Utah and Colorado, which have contributed nothing so far in terms of football, and, tellingly, its options seem to be gone, unless it wants to reach down for a Nevada school.
So, where does that leave us? Well, effectively, the B1G would have to pick up an even number of schools that fit its criteria to make expansion feasible. For the sake of argument, we can throw out any SEC (except maybe Mizzou) or PAC-12 school for obvious reasons. That leaves us with maybe Kansas, maybe Mizzou, a couple ACC schools that fit the criteria of not being central to the conference like Pitt, and the crown jewels of UNC, UVA, UT, OU etc. as pipe dreams. Now, assuming we are probably only looking to add two more schools (no major conference has gone to 16 yet, presumably for the reason that no one wants to be the first to try and fail at it), let's see what the options are.
So, let's talk about the smaller, more doable, options of Mizzou and Kansas. Neither have historic football, and don't add new demographics as the previous moves have. Same with Pitt. Syracuse doesn't either, and isn't in the AAU. The problem is that even if one of those schools seemed OK if the goal was to help get another school, the schools that really bring in the bucks and prestige are all in larger groups. UT and OU go nowhere without each other, and both of them have their own baggage of the other schools in their states that they are likely yoked to. Similar with the ACC schools. UNC and UVA are probably together, and both have schools in their state that are not appealing options for other conferences to pick up, and would be left homeless if the ACC broke up - not to mention the power they lose by going to conferences where they are one of many, not the stars. Similarly, now that the ACC has 15 schools, it becomes an issue of where all those schools go. The upper half (Clemson, FSU, Miami, Duke, etc.) is appealing enough to get picked up by other conferences like the SEC, but the problem is that the SEC only has two spots left as well, so some school is left out, and the Big 12 might be reluctant to spread its geography further. Basically, the stronger members have no incentive to leave, and the weaker members will do anything they can to keep the conference together.
So, if the B1G is looking to add schools that are contiguous, academically acceptable, and bring demographics or money or football, the problem is that some schools that are singly available really don't do it, and the ones that do do it are in groups such that the conference would have to be willing to go over 16 members (which is not impossible, but dangerous). Now, if some other conference is the first to move, and other options are on the table, then all bets are off, but as it stands, there is little incentive to be the first to move, and we may very well have reached a stalemate for the forseeable future.