It seems that there is no correlation at all anymore so it may not be a good time to get into Ethereum right now until the bitcoin fork happens. As has been mentioned, interest in Bitcoin is now at a high because of the potential for free BTG coins due to the fork.
I think that there has been a decoupling of pretty much all alts and Bitcoin over the last month or so. It seems to be in a league of its own. Certain alts e.g. NMC and PPC were heavily reliant on trade from within BTC-e. Since that went down the prices struggled, and with the birth of WEX there is still too little activity in that space.
ETH seems to be full of promise, perhaps it will pick up again soon. Still can't believe that BTC hit the highs that it has.