I'd at least let things shake out for April and then make a decision. Waiting until mid June is a long time to improve the big club. If you're bringing up Mayer and he becomes a guy who fills in at SS/3B/2B and Anthony and at LF/RF/DH, someone is either injured or underperforming. Hard to move on from Romy as he's the only backup 1B. Hamilton is the bench speed guy, but I think Mayer would be a big upgrade even if he's not getting full playing time. Anthony easily just takes over Rafaela's slot.
Bregman probably opts out this offseason and it makes it easier to slide Mayer in at 3B next year. Breslow just never figured out how to deal with Story and Masa, two guys that won't be here long term and are in the way of long term BOS guys (Mayer and Devers).