I think BNB is a temporary solution for the high fees, it doesn't compete with ETH on decentralization, when ETH solves gas fees BNB will lose much of its purpose.
I do see an interlinked multi-chain future with ETH being the central store of value, and with BTC fulfilling the role of gold.
So the most likely scenario is that ETH isn't going to die in the foreseeable future.
ETH is more decentralized, but it's equally as vulnerable to regulation as BSC, making the decentralization difference negligible. Also the DeFi/NFT traders don't care about decentralization; they only care about an open system they don't need to KYC to use, which you don't need much decentralization for.
A bet on BSC is basically a bet on Binance, for as long as Binance is a dominant player, they will always be able to get users to swap to BSC off of ETH.
ETH can't even handle one chain, nevermind interlinking others; how that's plausible to you is beyond me.
ETH 2.0 and L2 scaling solutions are more than enough for a multichain ecosystem.
I dont see enterprise level investors putting money on BNB, its an exchange coin. BNB is a temporary hack for small retail investors and pump and dump schemes.