I am all for a vanilla server experience but I really hope they will decide to somehow include the new classes if they do use the old school talent trees. I would, of course, understand the inclusion of the new classes if going back to old school talent trees will be happening. The Death Knight can just have a tacked on the lore of WC 2 knight variants and since monks have existed in the form of wow NPCs that should not be a problem. Also, there were Kaldorei demon hunters as well so I do not see how lore could not be added to include old-school demon hunter factions for the Demon Hunter class.
Including some of the more popular QOL and visual optimizations like transmog and hide of helm and shoulders is something I hope also makes it to the new classic servers.