Update: Apparently when Blizzard said the beta would begin "this week," it meant "today." Invitations are already going out, and people are playing it on Twitch, if you haven't received one yet but would like to see what it's all about. Have fun!
Warcraft 3: Reforged, the remastering of the great Blizzard RTS that was announced last year at BlizzCon, will begin multiplayer beta testing this week. Blizzard said that the test will kick off with 1v1 and 2v2 matchmaking for the orc and human races, with the undead, night elf races, and more game modes, coming "in the weeks ahead."
A specific start date hasn't been set but Blizzard said that initial waves of invites will go out to people who pre-purchase the $40 Spoils of War edition. Forking your money over early (before the end of the year, take note) will also get you four Warcraft 3: Reforged Skins—Champion of the Horde Thrall, Emerald Nightmare Cenarius, Fallen King Arthas, and Daughter of the Seas Proudmoore—and bonus content for other Blizzard games including the Meat Wagon mount for World of Warcraft, the Third War card back for Hearthstone, a new pet for Diablo 3, the Jaina, Thrall, Anub’arak, and Tyrande characters for Heroes of the Storm, and some Overwatch icons and sprays.
Blizzard said that subsequent rounds of invitations will be sent out to additional players, "such as those who have pre-purchased the standard edition of Warcraft 3: Reforged." (Update: The studio has clarified that beta access will be restricted to those who pre-purchase the game.)
Warcraft 3: Reforged will include both the base game Reign of Chaos and the Frozen Throne expansion, and along with updates graphics will also feature extensive map modifications, re-recorded voice work, overhauled cutscenes, and will be multiplayer compatible with the original Warcraft 3.
When last we checked, it was expected to be out sometime this year, but the beta was also supposed to start in early 2019 and we're now two days from November, so I think a 2020 launch might be a better bet.