DLC still able to be purchased on older Assassin's Creed games after Servers shut down?

Purchasing is done through the Microsoft store on Xbox. They are only shutting down the multiplayer servers.You’re thinking of a delisting which happens usually when music, car, plane or other IP licenses expire, which as far as I know is not a problem for AC games.

If you’re worried buy the x Ezio collection and the other remasters. Problems solved and you get better versions to boot

Yes you can still purchase the DLC, but any online modes and items contained in them will not be functional.

The Xbox One versions contain the DLC as well

Hi and thanks for reaching Microsoft Xbox gamer's community. My name is Josef.
I'm an Independent Advisor and a Microsoft Xbox user like you.

Hope you're doing great today Truegent10

Are you trying to purchase this DLC on Xbox One and newer consoles? Or Xbox 360?

You can try purchasing the content from here:
https://marketplace.xbox.com/en-US/Product/Assa...

But I can't guarantee that you can end the purchase, sometimes the old Xbox 360 marketplace is not capable of end the transaction

If you have further questions feel free to ask, greetings from another Microsoft user!

But wouldn't the in game store shut down as well cause I think it relys on the game servers?

The older Assassin's creed games really have some amazing soundtracks. Especially Assassin's creed 2.