According to Mike McMahon of College Hockey News, Notre Dame informed Hockey East that they will be joining the Big Ten in 2017. According to CHN's report, ND sighted "travel" as the main reason for switching conferences.
With Notre Dame on the way out, the league will have to look for a replacement in order to get an even twelve members. The obvious choice is Quinnipiac, a program that has become a model of consistency as of late. I am all for inviting the Bobcats into the league, they're a top team, they have arguably the best rink in the East, and are within driving distance for every team in the conference. However, I am not sure QU will leave the ECAC, even if given the chance. Look at this from their perspective- why leave? They're already the best team in that conference, they have had success on a national level, and they have developed some terrific rivalries, especially with Yale. A few years ago, there was no comparison between Hockey East and the ECAC but that is not the case anymore with Yale and Union winning back to back National Championships.
Assuming QU stays in the ECAC, my #1 choice for a replacement would be Holy Cross. In order for the Crusaders to participate in such a high powered league, they would need to update their facilities (or build new ones) but for the time being, they could play at the DCU Center, which is right down the road from campus. In fact, I believe BC is scheduled to play there next season. From what I can tell, Holy Cross has taken their level of play up a few notches under new head coach David Berard- at one point this season they were a top twenty team.
From a BC point of view, the addition of Holy Cross could help reignite a rivalry that has crumbled over the past twenty or so years (outside of the 2014 loss). There are a ton of BC fans that are passionate with regards to the Holy Cross rivalry and two league games every year would only add to that.