I believe they said in the live letter introducing the new PVP system that they wanted to give the trophy rewards about 2 series before adding new ones since they are thinking of people who just do a casual match or three a day or even a week vs the guy who is already level 30 and maxed out two 20k EXP bars at Crystal level having bought everything on the vendor and then some.

but we will see if more is added when Series 3 comes about next patch.