I am mainly in ETH, have a smaller BTC position because it will get legacy status as a crypto commodity; but shouldn't hold the top market cap spot forever. And very small allocations to a handful of the other larger alternates like SOL, DOT, ADA, etc.
At present I have been approaching the alt allocations in a naïve portfolio construction manner; just trusting the market to price them and collecting some diversification, since I don't have any alpha here. The positive carry on every position from staking or liquidity provision is really nice.
Regarding your thoughts about the race for second place; do you think there will be one dominant runner up to ETH and every other coin will get it's market share taken by it? One scenario I could see is that they all find niches and ways to integrate into the primary crypto structure; they all retain a following and specialization continues to occur as time goes on. In that case maintaining these allocations would be a good thing.
But if a winner-takes-all scenario seems much more likely to you I can see why you'd start reducing and consolidating into fiat. Perhaps it's wishful thinking but it seems likely that in-flows into the space will continue and it's hard to imagine these coins with decent capital already invested will be going backwards in market cap. Re-balancing back to risk targets is always a good thing, but I think this space is more likely to exhibit momentum rather than mean-reversion in the large scheme. So I haven't been too wary of continuing to add ETH since I bought at $2,700 through the current rally.