Animations, first touch mechanic, ball and player physics, passing, shooting, crossing, tactics and formations, goalkeepers, dribbling. If you look at every element of 2015 individually, there's nothing at all that they can do to evolve the elements without bringing back the movement mechanics from 2013. Essentially if they don't want to move away from this simplistic approach we will literally have the exact same carbon copy game next year, with slightly more varied crossing.
The things PES 2015 does so well, the first touch animations, the animations of the player movement transition and leg and foot planting, the physics of the shooting and passing physics so every pass and shot registers properly with appropriate animations, the tactical ideology of each team. None of this can improve at all without better, quicker more dynamic movement mechanics which where done in 2013
Unfortunately this is exactly what i think will happens, 2016 will end up being only a slightly better version of 2015. I think they may improve a lot the way the game uses the stats now since in 2015 is clear that the tactics are overuling individual stats and by doing that the players looses too much individuality. But i really doubt they will change the dribling and give the players the same freedom again because the lack of freedom is exactly what gives that old PES feeling for many players again, although most of them don´t even realise that.
The lack of freedom was something that always made old PES games balanced. In the past this was linked to the 8 movements lock and now, since 2014, it´s linked by the animations cycle, which is much better than the 8 movements but it´s still, IMO, a cheap solution to the balance problem.
During the 2011-2013 era the excess of freedom end up making games too difficult and "unbalanced" for the old era lovers, but for me they were going in the right direction. In 2013 they balanced the game making the teamates AI much more helpful and smart than previous versions and more important they made the game completely stats based, like you already said so many times. Making the gameplay completaly stats based the balance will be natural, like a player with a better passing will pass better than the one with a poor passing stat, never overuled by team tactics.
I think their dilema now is to make a game that can evolve to the point of a total stats based gameplay without loosing the balance neither the "old time PES feeling" that the lack of freedomg gives. Some solutions may be in the speed of animations being based on stats, like in 2013 (something also that you already said several times and IMO would create a much better individuality feeling than the way it is now), the improvement of teamantes AI and a higher variety of tactics (although tactics being very effective on 2015 they are extremely limitated to 4 or 5 styles of play).
If they can do these 3 changes for 2016 i will be very happy, even without total freedom. If they don´t, well, there´s always the next year...