A dedicated group of individuals have done what Blizzard has not: created more of the RTS Warcraft game in Warcraft: Armies of Azeroth.
Cards Against Humanity, Now With Less Direct Human Interaction!
Though technically, it's more of a remake. The creators are using the extremely deep Starcraft II engine and editor to recreate the original Warcraft III (and presumably its sequel The Frozen Throne, which came out in 2003). A great majority of our modern gaming existence is owed to the work done in Warcraft III, from giving us the major events we witness in World of Warcraft, to literally creating a whole new genre- the world's most popular- the MOBA, thanks to the Warcraft III map Defense of the Ancients.
According to the team over at moddb.com, they are focused strictly on recreating content with the newer engine. Though Blizzard released hundreds of WCIII assets last month, the team has opted not to utilize them, saying "We plan to use sounds and effects, but models are quite ugly."
Endless War(hammer), Part One: Our Guide To All Current Warhammer Titles
The game hopes to retain the exquisite unit and faction balance found within the original.
As for any new additions, such as the clamor for different factions such as the Naga or Blood Elves, introduced in World of Warcraft, they are leaving that to the rest of the modding community.
Given the constantly updated nature of WoW and the prolific story that is enmeshed within the game, it seems unlikely that we will ever see Warcraft IV, a return to the traditional RTS title that quite literally started it all.
In the meantime, we'll have to console ourselves with this. No word on when the mod will be officially released, but I'm making sure my Starcraft II is up to date, just in case.