Its odd, Earliest they could win a race most likely is 2021 when the new rules come into effect, but he is out of contract then and he will probably be eyeing Mercedes or Ferrari again.
Cant blame him, but done for the money I reckon. He must be thinking its better being number 1 at a mid pack team than being the next Mark Webber at Redbull.
Also cant be good for the confidence knowing your team mate is faster and is going to get faster also.