I have hourly data of a metric for 15 days, Can i predict the outcome values for same metric for the next 15 days?
If its a timer series data, then according to me you should go for RNN based model, typically LSTM.

Also you are looking an output for next "n" days, in this case you have to develop "Multi-Step LSTM Models".


  Please refer a very good link on TimeSeries problems
  
  Also you can refer TensoFlow code of very basic timeseries problem on
  github.


Note: Please modify code for Multi Step problem.