Considering one of these two articles is an interview with Kevin Morrison from the Fred Rogers Company, I'd say it can be considered "announced."
As for using cast members from the Neighborhood program, I think FRC was looking to do something new based on the old show and not just repackage what once was. I think there's a different market out there now and a totally different types of shows to compete with. This new program needed to be different but still, the desire was there to pay tribute to Fred Rogers through his characters and his practices.
I'll share my thoughts in more detail on the blog later this week, but I think they've hit the nail right on the head here by not trying to recreate Mister Rogers' Neighborhood but rather using bits and pieces to carry on Fred's legacy to a new generation which is looking for something totally different.