Although Agents of S.H.I.E.L.D.’s current and final season has shown that there are other methods of traveling through time (assuming you consider that series canon to the MCU film series’ continuity), it remains to be seen if time travel will be utilized in the MCU movies again. It doesn’t sound like retrieving the Infinity Stones again from other time periods as an option that can be turned to again, so we’ll just have to wait and see what’s in store for Phase 4 and beyond to learn if another opportunity presents itself that requires one or more of the big screen heroes to go into the past or future.