Well, we never know exactly what is the plan Elon Musk after this and what he can do for Dogecoin, might this will be another way to manipulate and help it grow up. We can't underestimate his influence, can do impossible things because of his money and make use of this platform to hype this project again. But, this never assures that it boosts the future of Dogecoin and I don't also think he could hype Doge forever, it still has an end.
Twitter is a powerful business instrument. In Eastern part of the world and Europe Twitter is not that much popular, but in States a lot of business is involved in it. Companies use twitter for free for their commercial purposes. Elon Musk plan to oblige them to pay for this instrument. I find it that simple. There is nothing to do with dogecoin or cryptocurrency at all. Regular users will continue to use it for free, as he promised. But companies will have to share their income now.