In my opinion its better to sell a part of investment and hold another part. With the hard fork / segwit battle, its difficult to know what the price will do, i suppose that if we had a fork with two chains prices will go down. But on long time, i think that we will have higher prices in one or two years.
In the long run the price won't be much affected, but in the short term this potential fork can turn out to drive the price down to possibly sub $500 levels. In that regard, it wouldn't hurt to liquidate some of your Bitcoin holdings to have a good sum of fiat aside for when the price reaches such low levels. Traders always prepare themselves for every possible scenario, and this whole fork situation is definitely not an exception.