I am going to hedge my bets, I will sell a portion of bitcoin pre fork and invest in alts, then I will sell another portion post fork to invest in alts (if the signs are looking good) and finally I will leave the rest in bitcoin throughout.
selling your one portion of bitcoin is a good choice. because anyhow after this fork the price drop and you can buy it again for less price. and investing in altcoins is best idea now all alts are dropped good time to invest.