If they trade Doncic, I think they will make the team take on Hardaway and Bertans as that would clear their cap a bit more.
I proposed this the other day.
Doncic, Hardaway, Bertans
for
Brown, White, Rob, Pritchard, Gallinari, Muscala, 24 1st, 26 1st, 28 1st, swaps in 25 and 27
So post-trade Boston would be (re-signing Grant)
Starters - Smart, Doncic, Tatum, Grant, Horford
Bench - Brogdon, Hardaway, Bertans, Kornet, Hauser, Champagnie
Open Spots - 4
That would be an interesting team. Its success would depend on how well Doncic and Tatum could get along. Given Doncic's ceiling, I'd probably do that, but it is a lot to give up and the team would need to do very well in free agency to make it fully work.