Apart from current contracts there's also the option of sign and trades to add a player (longterm) to the roster (which creates a TPE again for the other team). Some options next off-season:
Spencer Dinwiddie (Brooklyn), Josh Richardson (Dallas), Richaun Holmes (Sacramento), Victor Oladipo (Indiana), Evan Fournier (Orlando), John Collins (Atlanta), Lauri Markkanen (Chicago), Markelle Fultz (Orlando).
Some teams need the cap space for a big free agent (and have to renounce cap holds on their own free agent or sign-and-trade for a valuable TPE). Others are afraid to overpay for their free agent and would welcome a TPE instead.