Digging into the parts bin is very unlikely - there are plenty of out of service Type 8s with undamaged carbodies that can and should be resurrected first before the T resorts to that. Fitting out a bare parts shell into a serviceable car is not a small job, and unless they keep playing bumper cars with the fleet and availability drops far below minimum requirements, there is no reason to expend that much effort.
Fast "fixes" like reducing frequency of service, running single cars, and suspending service beyond Brigham Circle are far more likely - don't forget, strategies like these have been used before! "We don't have enough PCCs" - okay, kill Watertown service... "We don't have enough LRVs" - okay, kill Arborway service... "We've banged up about 30 cars in as many years" - what's on the block this time?