Bitcoin dominance is still superior, around 64% if you look at the btc-d chart on tradingview currently (rising consecutively in the last few days). At least they should be able to suppress dominance to the range of 45%-35% if we refer to the needs of the previous 2 altcoin seasons. Otherwise, we won't see a large number of altcoins outperforming simultaneously, maybe just a handful in turn until the bear market phase begins.

https://tradingview.com/chart/?symbol=CRYPTOCAP%3ABTC.D