If you see the graphics above is insightful and contains fact in this market, Bitcoin and Ethereum already shown their roles and next months will be for an altcoin season.
Don't be quick to forget that Ethereum is also an altcoin. So, when referring to altcoin season; ETH is also included. By the way, I don't understand what you actually meant by ETH outperforming Bitcoin when we know that Bitcoin dominance of the market is still above 51% while ETH has 16%. There's still a huge gap.