A couple of things here..
1. McAvoy isn't playing in Boston this year. BU will be in the tournament and the absolute earliest their season can end is 3/24. The Bruins would have 8 games left and I can't see them, and don't want them, burning an ELC year for 8 games. It is bad business. I could see maybe Bjork joining the team if ND loses early, but only if the B's need to use burning the ELC year as a sweetener to get him to sign. That's not happening with McAvoy.
3. The expansion draft. It is muddying the deadline. The Bruins are compliant and in good shape. They probably go 7/3/1, protecting Bergeron, Marchand, Pastrnak, Backes, Krejci, Spooner and then probably 1 of Hayes/Beleskey/Nash up front. Chara, Krug and Colin Miller on D, and then Rask. They've covered in the exposures as well, so they do have some maneuverability. The Bruins could theoretically add a player with term, and be able to protect them in the draft without too much trouble. An impact forward boots out Beleskey/Hayes/Nash who they can all afford to lose. Adding a D could be somewhat problematic, since you'd risk exposing a Colin Miller, but they can work around it. Any D they acquire that they'd want to protect, is likely an upgrade on Colin Miller and / or he'd be in the deal going out. A lot of teams aren't in position for this, which makes it difficult for teams to acquire a player with term left. Say find someone interested in McQuaid. That team would have to either have room to protect him in the draft, or risk losing him to Vegas. The risk of losing him would need to be factored into the acquisition cost. They almost need to be treated like rentals.
In short, I don't think they'll be able to move Kevan Miller, McQuaid, Hayes or Beleskey. Too complex to work out right now, but maybe they can move 1 before the expansion draft this summer. Right now, maybe someone tosses them a late draft pick for Morrow or Liles, but that's really all I can see in terms of selling. On the buying side, they can add without any expansion draft problems. I just don't want any expensive rentals. I could be talked into an extended Shattenkirk, but that's about it.