It'll vary. Much of the dominance Bitcoin lost was to cryptocurrencies we see in the top ten, namely:
- Ripple
- Cardano
- Tron
- NEM
- Stellar
- EOS
etc... So for it to come back to 50% dominance, those cryptocurrencies will have to give up some ground. How much ground will depend on how much people realize their initial run-up was irrational. Tron will likely get slammed. So... in short, depends on the altcoin. In general, at 50% dominance, most will be back to where they were around mid December, after Bitcoin crashed from hitting $20k first time.
Thanks for the quality analyses every time. I, however, disagree to this one. Another big factor is people's price memory - Ripple, Cardano, Stellar, ... have consolidated pretty strong resistance levels during the period while they go up crazy. You may say that they were too short period of time but if you look at their price charts, you would see their own way of consolidation happened. Those alt coins prices have moved up 4x - 10x since mid-December; they may give up 20 - 30 % (even up to 50 %) from the current high when this price churning gets settled down but I don't think they would give up entire gain since mid December.