Personally for Neymar it would be a good carrier decision, because the French league is much weaker than the Spanish one, so he could easily become the Triumphed Star of the team and country, with much less effort and playing difficult and heavy games twice a week, perhaps without getting kicked every minutes of each game.
Neymar is somewhat hated in Spain, disliked by the authorities, having been constantly under the bias of the referees and carrier-wise probably it is at least a "good try" to play in a different environment, where he might not necessarily be the constant victim of rough defenders are referees alike.
Neymar is a "party-man" loving to enjoy life and friends, of course he rather wants to be with 3-4 other Brazilians (including Alves who helped him a lot to accommodate in Barca) than being around Dennis or, Munir or the smile-less Gomes...
He knows that the useless players are still there, the Ardas and the Gomes types, and the management is sooo impotent, that if I were in Neymar's shoes, I'd also like to play somewhere else, where the management is capable of accomplish to needed rapid changes. This management (probably including the new coach) is just impotent and clumsy to do all that.
Messi was supposed to sign his contract by the US tour and I'm positive something is going on behind the walls, apart from Neymar's supposed departure...