This will be a good time to sell-- bitcoin is going down and people are just dumping on it. Meanwhile on the other side, people are getting the scraps of bitcoin that they can lay their hands on hoping that there will be a next bull run and make themselves rich. but if you are going to study the trend for this year, it is not looking good for the upcoming years for BTC. New coins are emerging and soon BCH will overtake BTC.
Bitcoin cash is one of the coins that is crashing the hardest, I really do not know how the coin that was forked is behaving because I really do not follow bitcoin cash that much but the chances that is going to overtake bitcoin are incredibly low, this is a good time to buy bitcoin or to hold it but not to sell it unless you love to lose money because that is what it's going to happen if you sell.