I really think, not right now, but definitely down the line, they should add some favorite races, subclasses, and feats from the main expansions to the Player's Handbook. Some of these options are just too good to pass up and some have become basically the default and most fun options for many players, especially when it comes to multiclassing.
Examples being:
Aasimar, Goliath, Kobold, Githzerai (We already have Yanki so adding their sister race shouldn't be too hard)
Oath of Vengeance Paladin, Hexblade and Celestial Warlock, Swashbuckler Rogue, Glamour Bard
Theres way too many good feats to really give an example
Maybe they could even do a poll to decide what to add from the extended material. I know that even if they do not adapt these, they have already and will continue to be modded in but it would be nice to have them as base options as well.
