Redesign will happen in Q1 2021 and Plaid will most likely be delivered by Summer 2021. There was a user on reddit who was an insider and was revealing a bunch of stuff, all of which has come true so far including 5% range boost in battery packs, model 3 with heat pump and new center console. According to him, a refresh for S/X will be in Q1 2021 with interior and exterior. Exterior will look like the mix of roadster and current S and interior will have more than two screens. He alleged that Model 3 will have somewhat of an update with heat pump, console and trunk but heated steering wheel won't be revealed until December.
This guy's account is now deleted and my guess is he got in trouble for revealing stuff. But that's my two cents. I just got a 2020 Inventory Model S with G battery and am quite salty about that, however, with these incremental updates I no longer doubt anything that account posted so expect a massive drop in value for your vehicles as a refresh happens in a few months. This range boost was the last update we were going to get before a refresh according to that insider.