My personal opinion is to hold the Bitcoins if you don't need the money for your everyday's life. Holding Bitcoins is maybe the best thing you can do with them. There are many factors of price increases over time, but the best one is Bitcoin Mining or lets say the design of the development of Bitcoin Mining.
After a predefined amount of mined blocks the mining rewards get halved, the so-called block-reward halving. At the beginning of Bitcoin there were 50 BTC reward per block, from end of 2012 onwards 25 BTC per block and since summer 2016 only 12.5 BTC per block. In 2020 we will se the next halving to 6.25 BTC per block.

So Bitcoin can be called deflational and thats very good for price increases. In the past, after every blockreward halving Bitcoin increased in price. It could be a while of low prices for Bitcoin this and maybe at the beginning of next year, but if we come closer to the blockreward halving it's likely we have a higher price for Bitcoin.