Seems like Kaskade got a new style of music... Not bad, just different than before.
There's a difference between "going mainstream" and "selling out". I have no problems with the former, as this just means he is getting popular. It's inevitable that good music will always create fans.
Now, I wouldn't approve if Kaskade were to sell out, meaning having the record label market the crap out of his music and have him sponsor random products and appear in ads purely for profit.