Now we can start doing predictions for Q4 of 2019 
Lol. Waaay too early and the predictions you'll get would probably be just random personal hopes of people who either want bitcoin to go to the moon or drop dead. Even the end of the 1st quarter would be hard to predict.
Never too early to predict
I see Bitcoin specialists who speculate about BTC price in 2025 etc. It's just the nature of the subject and happens often in the financial world - predictions are made. Also one year is considered as a short-term in finance. So, it might not be that early to start predicting and talking about Q4 of 2019.