Gee he participated in its writing...Thing is he is not in charge of the story. Story group is. And the Primary from my understanding is Lawrence Kasdan. Which is why he comes first in the writing credits.
We can only hope, though TFA has a very JJ style of reboot feeling to it. And he was constantly talking about his (empty) mystery box style for TFA and TFA delivered exactly that: Tons of unanswered question and a movie which seems to not make any sense. It certainly feels like tons of JJ influence.
So in the worst case Lawrence Kasdan is a JJ fan because that is financial working concept of selling mystery with actually need to come up with a solution for all those unanswered question. Those I am not that pessimistic as Kasdan has done tons of star wars writing in the past.