I'm not sure that I understand what you're suggesting. Is it that Anquan Boldin's skill set equates to seeing lots of jump balls? Is that even true? Particularly in our offense? With Belichick and Brady? I don't remember seeing that in SF, or any point when he was in ARZ. Perhaps you witnessed a couple of "jump ball Joe" moments in BAL that is skewing your opinion?
His last 3 seasons (all with SF):
85 receptions
83 receptions
69 receptions
All he'd have to do is act as another Givens, Llyod, LaFell, etc--although he'd certainly have more physicality and experience than any of them.
Boldin doesn't get much separation but is as good at fighting for the ball and winning it as they get. I don't think that's what they need or will go after. I don't really see them getting rid of LaFell because it would cost more to replace him, and that's whose position he would take.