Lego sets, mostly reveal the first official look of MCU movies, usually are leaked 5 months prior to release.
Doing the math, we might see the first leaked lego sets (hopefully with Namor and the new Black Panther) for Wakanda Forever in June
Edit: Following the pattern of Thor (though Idk if patterns do still exist), probably a teaser trailer to show it with Thor. That could be 2-3 weeks prior to release - mid June then.
I bet, they ramp up the marketing before or right after Thor - they have not much to promote in the 2nd half of 2022. Probably 2 months without a MCU project (if She Hulk won’t get delayed until 2023 as rumors indicate)
Trailer probably around D23 which will be 1,5 months before release.