According to the Athletic’s Sham Charania, Trey Burke will join the Mavericks for the rest of the season:
The Mavericks will have the available roster spot, since Willie Cauley-Stein has decided not to join the team in Orlando, also per Shams Charania:
Though this Willie Cauley-Stein news seems to have come out of the blue, many NBA players and their partners plan to have children during the off-season, which would be in July in a regular year. In 13 games this season with Dallas, Cauley-Stein averaged five points and just under five rebounds in 12 minutes per game.