Mojang have revealed two screenshots from 4J Studios’ next gen console versions of Minecraft. They’ve also shown the same scene from the current generation consoles so you can see the difference.
These two screens are from the PlayStation editions, with the PS3 version top and PS4 version bottom. You can see that the ‘draw distance’ on the PS4 is better, meaning you can see things further away. See how you can see the trees in the distance on the left and right of the picture on the PS4 version but not the PS3.
Similarly on Xbox, the Xbox One version has a much better draw distance too. In the Xbox 360 screenshot you cannot see the mountain in the distance to the right of the picture that you can in the Xbox One screenshot.
So the graphics on the next-gen consoles will be better, but not by much. The worlds will be much larger though, 36 times bigger in fact. They still won’t be infinite though, unlike the PC version which can support worlds that never end.