I love how people just slash and burn with topics like this.
Outside of a significant multi-year waiting list for season tickets, it would have to be a large donation for that specific purpose, probably upwards of forty million. For the 2008 expansion, the waiting list was said to be at 12K. I am sure other considerations would be worked into that decision, with parking being a main one.
However, I think way before that type of expansion happens, they will add in luxury boxes and redo the press box. Luxury boxes would be a cash cow, and if we hadn't had the recession in 2008-2010, we might have seen those already built.
Regrading the north endzone would be a major project, particularly since Sutphen Road would need to be closed or re-routed for the construction to occur. I doubt we see that unless there's other expansion involving the north endzone going on.