Can Bitcoin remain dominant without offering more utility?
Why not? It worked until now and I don't see why it should change. Nowadays its primarly store of value and it still works good for payments so imho that's enough.
Are utility-based altcoins the real future of crypto?
Nope, because for 99.99 there's no real use (except making theor creators rich).
Where do you see the balance shifting over the next 5 years?
Seeing how bitcoin dominance more or less consistenly goes up, I don't think that anything will change regarding that.