I imagine there will be a Training mode, even if it's as basic as the one in PES 2008. I'm hoping they definetely develop it though, having a Training mode is a nice touch to the game and it could be a great add-on if they put enough depth into it.
Having rewards again for completing training challenges. Bringing back the PES Shop would be a nice touch as well, and much needed I think. A real PES Shop, with options to buy an additional kit, giving the player the choice of editing and choosing a team's 3rd kit in a match. Additional balls, boots, and even pitch textures would be alright. Another good buy would be alternative training bibs to wear during training, or even having the option of no bibs and a training kit for a team.
Even a few novelty challenges in Training mode would maybe spice it up a bit more, such as trying the "crossbar challenge". Or having to re-create epic goals that have taken place in football history, e.g. Beckham's free-kick against Greece etc.
Just a bit more depth is all I'm asking for.