Altcoins take a huge dive in the upcomming weeks of the fork and recover at some point after the fork. Thats the pattern we've been seing. The problem atm is the steady stream of forks thats being announced.
These things move in cycles. The ICO rush, and to a lesser extent the ERC20 airdrop rush, both helped fuel the ETH bubble and to sustain the current price levels. I think that's what we're seeing now in Bitcoin, too -- additional incentive to hold BTC due to airdrops/dividends.
One thing to keep in mind this time around is that there is no replay protection on this fork. This might not be "free money" because it could come with a lot of confusion and lost money. I have a pretty good grasp of how to secure my funds and I know to be careful since there is no protection from replay attacks. But I'm still nervous. Hopefully Jeff Garzik comes around and they add optional replay protection back to the repository.