The major proposal of another token being added to Nostr is "in what way does the addition benefit every user?" and in that regard Bitcoin remains unchallenged.

However, if Nostr were to grow more, it would be natural for Ethereum to follow. From there it is a question of which DeFi solutions empower the Nostr ecosystem.

While most Nostr users aren't interested in Ordinals or Bitcoin Layer-2 solutions, it doesn't mean there won't eventually become overlap between those communities and Nostr.

Ethereum will work the same way. When people reach consensus that a specific utility is worth bringing to the Nostr ecosystem, there isn't much reason (and often no way) to stop them.

Idk dick about Solana personally, but I can easily see a future which ties npubs to Ethereum. It's just a matter of how it benefits users on clients that haven't even been built yet.