It's not really a question of "taking along" a current MB.
The poster does not have a current MB.
It's a question of whether a new MB should be purchased.
(And, a new MB can be purchased while a guest is inside any theme park as well as at resorts, etc.)
If (IF) the poster does not intend needing new on-ride photos/films (guests wearing masks) on the very few attractions that require a MB with a good battery (what is it, like 3 or 4 rides, total?) there is no need to buy a new MB. (Most of the WDW attractions that currently have on-ride photos do not require a MB with a working battery to access the photo.)
The oldest MB a guest might have from a prior visit will still work for all of the other important MB functions at WDW.