I think BTC's dominance recently has been due to the halving, once the hype dies down, I'd expect altcoin popularity to rise again
Now people are only interested in the good altcoins and bitcoin in this market, it makes the altcoins outside the top 100 have no liquidity like before. So the dominance of bitcoin is increasing and there is no sign of going down. In the future I think bitcoin's dominance will continue to rise