They are all playing well, and in the event of injury I'm sure that Pesonen would be the first to go, as he wouldn't be exposed to waivers. I think Caputi is likely a year away from a call up, as he's had a somewhat sluggish start compared to his playoff play last year. Stone is playing well, and is wearing the A here.
I believe the Taffe and Minard are playing well enough to warrant being called up as well, but with the depth at forward already in the burgh I don't see it happening unless there's a rash of injuries.
Plus, with the exception of a few, there's the waiver exposure to worry about even attempting to call them up. I think most of them will be here in WBS for the year barring massive injuries to the big Pens.