This kind of thinking gets repeated a lot. But it's fallacy.
Football stadiums, domed or not, are essentially useless for "year round" use for the simple reason that there are very few events that can book a space that big. Go look at the booking calendar of any domed stadium you want---it's hardly used at all.
And Buffalo already has a convention center that is underbooked. why would it build another nearly empty one? It's not a large convention destination.