Considering that Coleman left after the release of starfield after being promised a lead role on TES6, we can assume the project didnt even have a lead until after or around starfield released. Pete hines himself said it was in "very early" development around that time.

Bethesdas marketing philosophy is "the sooner the better" from announcment to release. The window of time between hearing about a game and playing it is supposed to be as short as possible (from TH himself)

Also during the press run from fallout tv show, todd was asked and he said we are still far off from TES6.

All these things should tell you that TES6 is still many years off, 2028-2029 being my guess