People leave bitcoincash because their block is still not perfect, so they prefer to go back to bitcoincore. And I'm sure bitcoin will reach $ 4000 by the end of this year 
Bitcoin has already touched $4000 this month ,so what will be the next prediction. 
It is good to have two scaling methods and if bitcoin cash have a good scaling solution then it will fly higher,there is nothing wrong in it,only time will tell how good both the scaling solutions are and since bitcoin is a house hold name when it comes to crypto currency,there is no surprise in seeing the price soar so high.