If Maryland expanded their stadium, all that would accomplish is allowing visiting fans of the top programs to buy even more tickets to further overtake their stadium when they visit.
I was in College Park two years, and Michigan fans had the whole upper deck. The same thing happened at Rutgers last year. I don't expect it to that extent this year, but I still expect Michigan fans will be at least 20% of the crowd.
As it is, I noticed that part of the deal with scheduling Texas is that the return game will be at the Redskins' stadium. I don't think there that many Longhorn grads/fans in DC or the Northeast as a whole, but I definitely suspect they'll have a strong turnout if their team improves over the course of the season to give them reason for optimism for next year and the fact that will be their first game NE of West Virginia (which is a tougher ticket) in a long time.