I don't believe there are any plans to make it available.
I've only seen Panasonic talking about putting it on freesat-enabled devices. In this statement, Panasonic say "the BBC have only made iPlayer available as part of the freesat service and there are no plans at present to introduce it to the Viera Cast feature."
So, kinda blaming the BBC, but in reality too cheap or too lazy to make the same arrangement Sony did to get it on the much cheaper BDP-S370.
Sucks, huh? I'd love to hear definitively otherwise.