The official word came with the release of NBC's fall schedule (here's my analysis), which has "Parenthood" returning on Thursdays at 10 — albeit one that will be given over to a new drama, "Allegiance," after the Super Bowl — while "Parks" doesn't yet have a timeslot, and will therefore be held for midseason (or in case another show fails).
NBC isn't talking episode counts yet, but I would guess that means that "Parks" gets 13 episodes to close things out, as we'll get to see what Leslie, Ben and friends are up to in the year 2017. And various published reports over the past week about "Parenthood" renewal negotiations suggested NBC was trying to reduce the cost for what's a very expensive show, given the size of the cast, so it could also be a shortened order, and the Bravermans go away for good right as "Allegiance" is entering.
UPDATE: NBC confirms that "Parenthood" is 13 episodes and out. Sounds like the "Parks" number hasn't been settled on yet.
All TV shows eventually end, but not all shows know that they're going to. Both "Parks" and "Parenthood" have had long runs — including multiple episodes in the past that were written as potential series finales — and now everyone will go into these seasons knowing it's the last time we'll be spending with Ron Swanson, Max Braverman, April Ludgate, Amber Holt and the rest.