Hello!
I have no guarantees of any of these things coming back into NHL 19. But as a veteran NHL player I would think that Winter Classic mode will be returning. I am unsure if it will be in Franchise mode or Be A Pro mode. Also I heard they are going to be working on new and improved celebrations to make your goal look even better. But as I said this is all speculations and none of this can be guaranteed.
Thanks, Zoie