I think the map is a bit misleading because it's going by place of birth and lumps metro areas instead of going by state. If you go by where they went to HS it's a different story because many of families whose players who were born in the north migrated south later.
http://www.maxpreps.com/news/J_G3Ol...ery-active-nfl-player-went-to-high-school.htm
You're right that NE has the population but I'm doubtful that a large scale culture change will ever happen. The NE was one of the original major recruiting areas from the early 1900s until the 70s w/ the Ivy powers back when they were still at competing at the top level. That has faded over time as other sports has taken hold along with urbanization and the entire region slowly turning into a pro-sports state.
It's the same by high school and with intra-state details:
http://Post original url/1edQH3K
Your maxpreps image (linked above) is also telling:
Connecticut high schools produced 24 current NFL players. That ties Indiana and beats Wisconsin, Minnesota, Iowa, and Nebraska -- most of which have a larger population than Connecticut. On a per capita basis, Connecticut is nearly as good as New Jersey and beats Pennsylvania and Michigan and Maryland as a producer of NFL talent. Ohio is the only B1G state that is distinctly better on a per capita basis.
It's true that the other New England states and New York don't produce many high level football players per capita. But I think the entry of the B1G to the region will have a big impact. Also, Connecticut, though doing well already (~10 BCS level players and ~2 NFL players per year) can do better, and will. High school and UConn football are rapidly rising in importance here.
Finally, the NE-NY region generally is indeed pro sports oriented, but Connecticut specifically is in love with UConn sports.
My point is that in terms of the recruiting territory it brings with it, UConn would not bring the B1G down. We are essentially at the B1G state average as a source of high-level football players; and if UConn in the B1G brings a greater emphasis on football regionally, in NY and NE, then we may even help the B1G recruit.