I think USPS is about to start a new contract for their mail cars so I imagine a bunch of Grumman LLVs to be sold. Here's an article that has some photos:
https://www.trucks.com/2018/03/09/usps-mail-truck-prototypes-vote/
TBH I've already see that Oshkosh Ford collabo but assumed that was just the "bigger" truck.