He's not wrong, but he's not right either.
Yes, shorter, and more episodic gaming experiences will, in all likelihood, become more prevalent over time.
However, and this is a big but, they won't be replacing the games that were always going to be massive anyway. Because the thing is, it's not really about the size of the game, it's about the studios making these games having the necessary skill and resources to fill them with content that provides satisfying pay offs in both the long and short term, so that you can go in, play for an hour, have an amazing experience that leaves you wanting more, and then likewise make sure that these experiences build on themselves for hours on end culminating in an overall high point (or points) rather than growing stale as you go along.
So of course, it's much easier to make more bite sized gaming experiences that are enjoyable, but there will always be a place for the massive games because, frankly, they are simply a higher craft when executed well, and that shows, and it captivates people.