BC, BU et al formed Hockey East when they didn't want to be in a giant (17-team) league with the Ivies (who, at the time, were widely thought to be considering their own league). Even though the Ivies have since shown a willingness to be in a larger league that is willing to accommodate some of their scheduling, length of season and admissions requirements, I don't see that being reversed. First, HE would be less willing to accommodate the Ivies than academically selective, small privates like RPI, SLU, Colgate, Union, et al and the Ivies would be more concerned about large publics + BC/BU being dominant with scholarships, more flexibility in recruiting and larger budgets.
I also don't think the rest of the ECAC, most of whom have long histories in college hockey, have any interest in being in a league with AIC, SHU, Niagara, RMU, etc. with their small rinks, lower academic standards and minimal history in the sport.