It is very difficult to predict the perspective of a coin! The main criterion for which it is possible to predict the fate of the released product is its roadmap and the team that promotes the project!
The teams, the availability of product, the roadmap, as well as the development being made by the team are always actually the things to always look at with the product being in the center of it all. I know at this stage the market is still speculative, and even shitcoins tend to rise as well, but for 2019 and as well as long term, what would really drive in sustainable demand is the product backed token or coin, are usually the ones that would get in some huge demand pretty well. Talking about sleeping giants at the moment, I am thinking of COSS, ENG, SC and ADA.
Holochain is the biggest sleeping giant for me. If they can achieve what they are working on they can be "the new Bitcoin" in no time!
My sleeping giants for 2019 would actually be XCD, QRX for tokens that will be popping up based on the fact that they are exchange tokens but for existing ones, I am actually looking at Cardano. This is one coin that has really been sleeping for a while now, and there is every chance that when this guy wakes up with a huge bull run and full market recovery, it is going to be a pretty huge one. However, we cannot always tell how things will turn out exactly, so one way or the other, we will just need to be patient and then see the way things would go.