Yes, they finally cast the mad Titan from the end credits of the first film. Though it's notable that Josh Brolin is only listed as voicing Thanos, which implies he will not be mo-capped for the role, as James Spader will be for Ultron and Mark Ruffalo was - somewhat - for the Hulk.
It's a fair enough consolation prize for not getting the Batman role. Two movies people actually want to see instead of one that they stare at like a potential trainwreck.
And I suspect this'll serve as yet more evidence that no, we don't hate every comic-book casting choice. Just stupid ones, which this assuredly is not.