We're already in a bull run already, and we don't know how much longer it will last. Depends a lot on whether BTC is able to hit $10k.

To me, it actually signals that the markets are quite overheated, and will probably correct very soon.

Instead of money being in BTC, the rest of the crypto markets are preferred as an investment at this stage. This means that a lot of people are in the crypto market right now for quick profits and will unload quite easily, instead of holding for the long term.

Bitcoin dominance usually decreases in a bull market, and increases in a bear market. Just look at how quickly bitcoin dominance decreased in the month of December. Sooner or later, the Bitcoin dominance index will have to return to its resting place, which in my opinion is around 50-60% naturally. That'll happen as soon as this bull run ends.