I had meant to post this earlier, and originally, I intended to start a college sports blog with a post on this topic. Unfortunately, I've run into some technical difficulties on the blog (which may or may not get fixed if I spend some money, but I'm trying to avoid that), so I'll post here.
Someone (I forget who, and I'm too lazy/busy to go back and recheck) suggested that realignment this year will be the most significant since the Big Ten added the sport in 2014. This year's realignment has been spurred by two issues: one specifically lacrosse-oriented, the other not.
As to the latter, the CAA lost James Madison to the Sun Belt Conference and FBS. In response, the CAA has added four new members. Three of those new members sponsor men's lacrosse: Hampton (primarily a member of the Big South, but played men's lacrosse in the Southern Conference), Monmouth (MAAC) and Stony Brook (America East). The America East also lost Hartford, which has downgraded to Division III. In response, the America East and MAAC both recruited new permanent members from the NEC -- Bryant and Mt. St. Mary's, respectively -- both of whom play men's lacrosse.
Meanwhile, in a move I'd been predicting for a few years, the Atlantic 10 decided to add men's lacrosse as a sponsored sport. The A-10 had four permanent members who played men's lacrosse -- UMass, Richmond, St. Bonaventure and St. Joe's -- so they would need two affiliate members for men's lacrosse to get an AQ bid to the NCAA Tournament (more on that later).
These moves reduced two conferences, the NEC and SoCon, to five and four men's lacrosse-playing members, respectively. Further, the NEC's remaining affiliate member, Hobart, was eyeing the A-10 as a possible landing spot. Seeing the writing on the wall, Jacksonville and Mercer both bolted to the A-SUN before that conference had even played a conference game (note that Jacksonville is a full member of the A-SUN). The A-SUN expanded further when two new Division I schools upgrading from Division II with existing men's lacrosse programs -- Lindenwood and Queens University in Charlotte -- both joined the A-SUN, the latter as a full member and the former as an affiliate member (Lindenwood's primary conference is the Ohio Valley, which does not sponsor men's lacrosse). Meanwhile, VMI, one of two remaining lacrosse members of the SoCon, went back to the MAAC, where they had been an affiliate member from 2003 to 2013. The MAAC also added three remaining teams from the NEC -- Long Island, Sacred Heart and Wagner -- as affiliate members (of note, this agreement apparently runs for only two seasons). The combination of all of these moves ends both the NEC and SoCon as lacrosse-sponsoring conferences at least for the short term.
Finally, the A-10 announced formally that it would sponsor men's lacrosse, taking High Point and Hobart as affiliate members to go along with its permanent members. That leaves Merrimack as the only unaffiliated Division I program for next season, although they're still in the process of transitioning to Division I, and ineligible for the NCAA Tournament as a result, so that may not hurt them.
Conference alignment for the affected conferences moving forward looks like the following:
Bryant (from NEC)
Air Force (affiliate)
Cleveland State (affiliate)
Jacksonville (from SoCon, full member)
Lindenwood (from DII, affiliate)
Mercer (From SoCon, affiliate)
Queens University, Charlotte (from DII, full member)
Robert Morris (affiliate)
High Point (from SoCon, affiliate)
Hobart (from NEC, affiliate)
UMass (from CAA, full member)
Richmond (from SoCon, full member)
St. Bonaventure (from MAAC, full member)
St. Joe's (from NEC, full member)
Hampton (from SoCon)
Monmouth (from MAAC)
Stony Brook (from America East)
Long Island U (from NEC, affiliate)
Mt. St. Mary's (from NEC, full member)
Sacred Heart (from NEC, affiliate)
VMI (from SoCon, affiliate)
Wagner (from NEC, affiliate)
Fwiw, I think more realignment is coming eventually. Specifically, I think the A-SUN and MAAC are too big to continue in present form, especially with each conference having a sizeable number of affiliate members. Further, given the importance placed on OOC scheduling, as well as the fact that both conference champions are in significant danger of a play-in game, I think there will be pressure in both leagues to get smaller. At this point, the NEC (four members) and Horizon League (three members) are the two conferences with the most lacrosse-playing members not sponsoring the sport. I think one possibility is that those seven schools could form a lacrosse conference under one banner or the other. Eventually, I could see both conferences sponsoring the sport, and thereby forcing expansion of the tournament to 24 teams, but I think a few additional programs will need to add the sport or upgrade from Division II first.