If you look at the UK version of NBA 2K17 on Gamestop you can see the accidentally leaked info of the Pre-Order bonus. Here is what it says just in case you can't access the website for some reason:
Additional Content
Early Tip off also includes:
5,000 Virtual Currency
92 Dream Team playable in quick game
Paul George USAB Jersey
My Team Bundle (3 packs)
and more!
So it looks like the 92 Dream team is going to be in the game if you Pre-Order it. Could this also mean Charles Barkley is going to be in the game and possibly with the TNT crew? We will have to see.
EDIT:
They just released all the info officially, so here it is: