Well, looks like bitcoin going over $6,000 today while most alts are on red is due to people moving into BTC to get the fork coins. If so, after the fork we can expect money moving back into alt coins and BTC to come down somehow.
How do you know it has anything to do with the fork coins? Anytime that the price of BTC rises with high volatility, altcoins usually suffer. This was expected with Bitcoin making new all-time highs today. The same thing happens when BTC price crashes -- alts are bloody.
Altcoins usually thrive when BTC price is sideways/consolidating. Considering the recent volatility, it could be weeks or even a couple months before I think we'll see altcoins enter new uptrends against BTC. That doesn't mean that the bounces aren't worth trading -- they are. But I would be very cautious about building long term altcoin positions in the short term.