Two unnamed episodes have been confirmed for Season 5: one in which Bloo is stuck with Madame Foster in a fabric shop while everybody else is at the fair, and one that will have lots of singing and music. Both were confirmed at the Comic Con last year, and the latter was directly alluded to in the production blog. I already said this, but I'm crossing my fingers Frankie will be heavily involved in the latter, for obvious reasons
Aside from that, nothing is known so far. IMDb is potentially even less reliable than Wikipedia, because there is tons of false information that CAN'T be instantly removed. And the official blog hasn't been updated at all since last October.
Personally, I like to think that they're aware of our deep affection and devotion to Frankie, and are revising and altering the upcoming episodes to make Frankie more prominent and thus make us happy.