considering that Gold (less commercial than HS4) did 23cr, while clashing with a movie that did 19cr, on a holiday that is smaller than day after Diwali, it should be getting to 33-35cr.
also, looking at Golmaal Again which didn't have a great trailer or good songs (except one), and had very late advance booking, and still did 30cr opening day (with a small clash), we can see that these comedy franchises/family entertainers have big potential with the walk-in crowds.
the big differentiating factors here are that Golmaal 4 was coming after a hugely appreciated movie, and Housefull 4 is coming after shitty Housefull 3. but HS4 also has GST advantage.
unless the trailer is totally horrible, or the movie is so bad that terrible WOM spreads like fire on day 1, it should at least clear 30cr.
it won't reach the Khan day after Diwali numbers though (36cr, 39cr, and 48cr).