The overall theme really hasn't changed over the past year. Bitcoin grinds higher, pumps out new highs....consolidates and even pullbacks and then does it all again. This while alts, outside of really one move have continued to make no, or just one all time high.
Ethereum is a prime example of this and Bitcoin continues to outperform it.
Plenty of room for BTC dominance to increase... 
Granted with more cryptos and plenty of big name alts these days compared to 5 years ago, dominance was still as high as 65% recently and could easily shoot back up there if bitcoin goes on a continued run with alts barely moving higher.
At some point alts will make a face ripping move as they always do relative to bitcoin, but who knows when at this point.
I will say, if and when it happens. I'm probably looking at it as a sign the market is at cycle top.