Gonna do this once.
Jojo is good player with great potential, he has talent but that talent does not guarantee that he will turn out to be a quality player. That's my stance on Jojo himself as a player.
As for him failing, well first you gotta look at the position of the teams that are chasing him, City and United. Neither of them need him, and are chasing him only out of sheer frustration, and if they are able to splash 30mil just like that they won't have an issue doing it, next winter/summer/etc. Once he goes there he will need to adapt to the style of play in England which is significantly different than in Italy, not to mention that while he is adapting there, he will have tougher competition then Llajic or Rossi, he will be competing for spots against the likes of Nasri and Kagawa (I won't even name the David Silva's and the Rooney's). Now fast forward to mid-season or end of the season, City/United will realize he don't fit nor is he needed and that they've rushed their decision to go for him, now he will spend the rest of the season on the bench. And Beppe will swoop and get him for significantly cheaper.
As for the whole talent thing, you can have all the talent in the world (see Quaresma) but that don't guarantee anything, nor does it mean you are a good player. And the way this guy is overrated here is absolutely ridiculous! He hasn't carried his team, nor has he done fuck all, he has potential but he is in no way a Di Natale who could carry his team or even stand out(at least for this season).