I think some of you are vastly underestimating the travelling public re TUI MAX.
Did you read the TUI social media accounts pre the grounding?
I suggest you do, so have a look at their Facebook and Twitter back in March, both of which exploded with 1000's of TUI customers who were wanting to cancel and the pressure from them on TUI to do something was immense - The groundings followed within 48 hours when the CAA and EASA decided.
Things are different now to the days of the DC-10 etc...(40 years ago)
TUI UK Holidays have for many months now wiped clean on their media and online web pages for both Holidays and Flights (and Our Fleet info) any reference to the fact TUI operated the MAX, or in fact that have any at all. (8 UK reg'd a/c grounded in UK and 1 in TFS plus a load more brand new ones parked up at Boeing)
Therefore the likelihood of TUI re-branding their aircraft when a RTS is effected is probable. (Ryanair have now used the tag 737-8 200 for their new fleet, having painted out the word MAX on their completed aircraft parked up at Boeing)
The MAX tag has tainted the 737, and will never be used on any other new Boeing model aircraft.
TUI may quietly just release their 737-8 and 737-10 back online as a 737 when the ban is lifted - dropping any reference to MAX.