He is now going to fulfil his potential, we will see an all around Neymar as a player like we see him with Brazil.
Sadly, here with Messi he couldn't have developed at 100% of his possibilities: it is true that the linking and partnership of the two on the football pitch was amazing, but Neymar's potential would have always been limited because it is obvious that, as long as he will play, Lionel Messi will always be the main man at Barcelona. And there is nothing wrong with that, it is something Messi deserved and deserves for what he has done and still does for football, even Neymar himself knows this very well, admiring Messi as his idol and the best player has ever seen.
But Messi is 5 years older and Neymar is not a young talent anymore: it would have been stupid from his side to "waste" the prime of his career in Messi's shadow also for all the years to come, so I think that, by his point of view, he made the right choice.
And I think that it is the right decision even for Barça (if they manage to replace him properly), because Neymar, without a leading role, would have played far from his best (like the majority of the last season), proving to be detrimental both for Barça performances and his own career as well. Not a single one of the players who are named as potential replacers of Neymar (Coutinho, Dembele, Hazard, Dybala or whoever) are worth Neymar's skills and pure football quality, but there is a high chance that they will fit Barça better than what a non-motivated Neymar could have done.
I am sure that, starting the new season, we are going to constantly see Neymar playing at his very best.