my prediction is that in ten to fifteen years capacity will be 10,000-15,000 seats less than now. new data shows college football attendance down by second sharpest ever. nfl down. and parents are keeping their kids from playing.  with better flat screens and slow motion why waste 6 hours fo your weekend going to a game when you can watch at home in 90 minutes without commercials or halftime.
the future is going to be less people wanting to go to games so how are you going to get people there? they are going to make the seats much bigger and wider, more aisle space and more aisles, eventually will feel like going to new movie theaters with reclined seats. food will be delivered and will be restaurant quality not game quality. you'll eventually have at every seat a replay monitor or between every two seats with rewind capabilities so you can rewatch. basically the model they have now of packing people in crappy seats is dying and old. new wave is to make people want to go the the game and be comfortable.
so in ten years, mark my word, there will be a contraction of seats and more, wider aisles added. concessions will be ordered from the seats and delivered. comfort and experiences will be the selling points not the game itself. otherwise, why would i leave my house to pay money for uncomfortable seats, horrible food, high prices, and long waits while sitting outside?