BTC.D was rejected from the channel's trend line and consolidated above the 55% zone (blue). It then broke down and found support at the 54% zone (green).
If BTC.D falls below this 54% support, it could drop to the 53% zone (yellow), which would be positive for altcoins, as a lower BTC dominance usually benefits them.
However, if BTC.D bounced back from the 54% zone back to the 55% zone, it would be very bad for altcoins, as previously BTC.D bounced many times from this zone. Increase in dominance causing further declines in the altcoin market.