What does this mean for the future of h game development ?
It depends on what you want. AI is certainly able to create decent single images and backgrounds. The main issue right now is to create a consistent style across the game or even just across the same character within a story. The images above illustrate that perfectly, as there's little consistency between them and it looks like they've been made by several different people, while only one of them looks remotely, like it could have been drawn by DC. That's why, right now, you'll never really see a whole series of the same person in different situations, etc. - unless you feed the AI with very well prepared images. Next to that it doesn't seem to be easy to get excatly what you'd like to have, so you may tell the AI to create X but it'll only do it 95% the way you'd like to have it.
So we'll likely need a few more years until AI is really able to replace some parts, so I can't really judge when we'll actually reach the point where AI will be able to be consistent enough and will be able to provide excatly what's wanted.
The "beauty" of 2D games is really, that even the smallest detail is totally up to the artist. There are no practical limits, as long as the artist has got the skills it takes.