I'm definitely not an expert here, but I don't see why BTC will go down right now. It's a volatile market, and the price will continue to go up and down as it usually does, but the trend continues to look good for the long run, so the price should continue to rise. Selling 70% isn't just to much? Also, right now users seem to only be dumping BCC, and I don't know how many users will get more BCC after Poloniex credits them, but the dump will probably continue. And yes, probably a pump after that, but I'm not sure it will affect BTC to much.
Right now, since the long run trend seems to be for the BTC price to go up, I will just keep investing from time to time, and then holding.
That's not too much if we have a financial back up in my opinion,
other reason : have you heard something like another chain split again in the coming months or so ?
that is also one of my reason,if it's true than we will see another pump and then dump movement 2 times before that.
i am not saying we sell 70% all of our Bitcoin into fiat when we hit $3500 marks,but total sell 70% all of our Bitcoin beyond $3500.
for example : we hit $3500 marks today,that mean in the coming days we can hit another marks higher or lower,then sell 10% from it in $3550.
after that higher again sell some of it and so on.