That seems to be the suggestion from CapFriendly.
Basic Formula
This formula is used throughout the season and during the off-season
Amount team can exceed the cap = Cap hit of LTIR player - Amount of cap space available
Basic Formula Example
The league upper limit is $69M. A team has an averaged club salary of $68M and a player with a cap hit of $5M becomes injured and the team places him on LTIR. The team is now permitted to spend up to a new limit of $72M:
Cap hit of LTIR player is $5M
Amount of cap space available to team = $69M - $68M = $1M
Amount team can exceed the cap = $5M - $1M = $4M
New limit = $68M + $4M = $72M
https://www.capfriendly.com/ltir-faq
So the roster moves tomorrow might be pretty fast and furious.