He still might not come, if his wage demands etc are too high which is what is rumoured. We will have to wait and see.
To be honest, i think he is a stop gap until we can sign Falcao, cant see him getting masses amount of game time, but we are signing a proven goal scorer in the premier league who is in good form at the moment, so even if he scores 10-15 goals for us this season he will have been a good signing, IMO. But for next season, i doubt he will be first choice. Still, its good to have options, which we have very little upfront at the moment.
I think he will get game time this season, but obviously will have to compete with Torres. Torres hasnt been that great so one of two things will happen, either Torres starts banging them in and Ba wont get in the side(which is good for us, not so good for Ba), or Torres continues to langish and Ba will get plenty of game time(and hopefully continue scoring). Im confident he will do ok with us, with our creative players like Mata he will surely get plenty of chances.
I cant see Rafa playing both of them at the same time(unless we are in desperate need of a goal in the last 10-15 mins), as it would mean changing to 442 which we then cant fit in all our midfield players.