Not in comparison to the 3e/4e eras. There are what 2 additional player facing rules expansions since the PHB in this edition, there were more than a dozen in 4e alone. There is certainly more room for lore books like Mordenkainen's, on these forums alone there are people screaming out for Planescape, Selljammer, Greyhawk, Darksun, Dragonlance. Throw in a adventure path for each of them and a couple of player facing books to consolidate the setting specific subclasses for a general audience and there is enough material for the next 5 years, or more, at current rate of publication.