It looks quite difficult to get into that phase again, now we can see where BTC dominance is already very large in the market, I think ALT season will come when BTC dominance decreases maybe in the range of 50%, so you can estimate if BTC dominance decreases meaning ALT season will appear soon.
Do you really think that Bitcoin is ready to let its dominance go for now, I really don't think so, and I don't see much reason why we should be relying on Bitcoin dominance for these coins to increase in value, I think that they all have their own different use case which many of them he even claimed in the past that they have a more useful platforms than that if Bitcoin.
Ethereum is still a good project and I don't think they really need Bitcoin dominance to reduce for them to really increase if they mean business like they meant it in 2017 when they made their platform conducive for both investors and developers to use, but the platform they currently have has become a living shadow really as investors are no longer finding it attractive.