WWE will sell anything in their shop that they are allowed to. That is not limited to only talent who are still under contract.
Brock Lesnar and Sting are examples of Superstars who had clauses in their contracts saying that the company couldn’t sell their merchandise after departing. That is not the same for everyone.
WWE Shop is still selling a Dean Ambrose t-shirt on their official shop. The rule that they must take down merchandise 90 days after a contract expiration is only applicable in certain situations. Obviously, they are allowed to sell Dean Ambrose merchandise until it’s all sold out. The company also recently re-upped their trademark on that name. They currently have youth sizes small and medium in Ambrose’s “Never Apologize” design.
Dean Ambrose isn’t the only departed Superstar who has merchandise on WWE’s shop. The company is also still selling merchandise for Zack Ryder, Rusev, Deonna Purrazzo, Zelina Vega and more.
You can check out some screenshots below that were just taken from WWE’s Shop. A lot of the released Superstar merchandise is now on clearance, but it’s still available. Interestingly enough, it seems that the Deonna Purrazzo and Zelina Vega merchandise is a custom print situation.