The jokes about Howard's lack of a doctorate began to escalate when Bernadette achieved hers, and it's time something was done for him. Throughout the show he's suggested that he'd never been bothered by the torments, he knows he's smart enough for one, and knows that having a Masters degree from M.I.T. is nothing to scoff at, despite Sheldon's attempts to rubbish it. He is also able to say that he's an astronaut, unlike any of the others, which is arguably more impressive, but he's still haunted by the lack of the title. But in Season 8, Howard did take Sheldon's graduate class in sympathy and that could imply that Howard is thinking of getting his PhD after all, even if it is just to get Sheldon to shut up.