the percentage of btc domination has been only one way.
while not the whole story, unless btc can sort out the segwit, then LN, and make block size about 8MB/16 M as Coblee seems to think 400M users can be served with 1MB/segwit/LN, but still to expensive, so we need 8MB to 16 MB blocks at least to make it usable.
ETH shows just how much the market share can be taken.
Btc may have advantages being the settlement layer.
That is very far from happening. Etherium cannot replace and overcome bitcoin. Though there are many problem behind bitcoin network but there are solutions waiting in-line to make bitcoin work better and stronger. If you look at the value of bitcoin you can say that bitcoin is still strong amidst the issues and will continue to strive and will continue to exist as the best crytpcurrency online.