(They have to be close to announcing it, as they're about ready to start taping the new season, correct? I guess they'll hold off until this season is finished- they've got 4 weeks left....)
...and then six-ish weeks (plus or minus a week) between that show airing and when the new season begins, given the show's current tendency to start mid-September.
Given the (likely) pretense that everyone being aired is up for the job (highly doubt that), they aren't going to want to say "it's Mayim" before LeVar Burton airs; same if they went off the board - as much as sports fans might delight in it, you don't want to announce Dan Patrick before Joe Buck airs after you've already promoted the latter.
Both Ken's first two weeks and the TofC (Buzzy) taped about six weeks before air per those episodes' slates (most other guest hosts have had larger tape-air gaps), and they could
absolutely do it closer if they needed to, especially with the show still utilizing a closed set (as has been the case since the pandemic first started).