While solidly behind bitcoin, I cannot be at the position of "only bitcoin forever".
Here is my purely behavioristic argument:

1. Wall Street (WS) largely "missed" bitcoin as more than 84% is already issued with very small (anecdotally) institutional ownership.

2. WS knows how to do "promotions".

3. Would it be easier for WS to promote a new token/coin/entity that is not almost fully subscribed yet vs the one that is already owned? I think that the answer is "probably, yes"

4. WS don't like chasing, but they do like sweet early deals.

Conclusion: BTC will be pushed first and will dramatically appreciate, but then the momentum might switch to "shitcoins".
Which ones's?
IMHO, the one's that are under-issued: XRP (since Ripple can make sweet deals at 40C now with appreciation later), watch out for Ripple issuing billions of coins from their 66 bil "stash", maybe ZEC as only 6mil out of 21 mil were mined so far. Don't want to mention newcomers, but watch out for large tranches of coins being allocated to WS hedge funds and institutions from some new and upcoming chains.

Personally, I don't think that ethereum would show large appreciation due to much competition in the area (POS) where it wants to compete.

One can, hopefully, design a strategy where potential profits in "shitcoins" would be transferred to bitcoin in due course.
I don't intend to sell any bitcoin (and certainly not for shitcoins), hopefully, until retirement or some unforeseen urgency, but some cash allocation along the lines that were mentioned above could be interesting. We shall see.