I think you can sell ethereum to buy solana and it might be long term or short term whatever, that is profitable strategy i think.
Btc is future gem in strong hand, i don't think you should to sell btc to buy instead of solana or any token.
solona is still very new. sometimes people feel hesitant to enter solona. that's because the hype is very strong, especially for a project that sells with the solona network. they soon found a good market.
if have more ETH I guess it's ok to share it with solona to keep up with the market hype. quite an attractive strategy for short profits. because solona is still a lot of development.
I'm not totally convinced selling some of my bitcoin and ethereum for Solana. So i won't have to deal with it and all its ups and downs. I'd rather focus on acquiring more bitcoin and ethereum when there are sudden dips than taking the risk of investing into an altcoin that has still no guarantee that it will also be a promising gem in the near future. Other people might take the risk of investing into it but never will i take that risk too unless it will make sense to me why i have to invest it because of its own worth and not just the hype that controls its value.