I've been playing Minecraft since its release on Xbox One, and I've spent with friends all this time on just a single world.
Today with so many updates that can not be applied to a old world, we become frustrated at being forced to start a new world to be able to enjoy all these updates.
Then came an idea that perhaps only seems feasible for a layman in programming. But I feel compelled to share it with the hope that the truth is indeed possible.
A World of Minecraft XboxOne consists of 25 maps in the form of 5x5. Even with countless hours of play, and nearly explored all these maps, in my case I would say that at most 2 or 3 of them contain essential constructions for me. If there was a tool that could LOCK this maps, and all the rest was rebuilt in an updated way, I would have a fantastic result in my game and a lot of people.
Ex: The maps would be named column of numbers and letters. Choose to lock a map to my taste, such as C3 or D5. They would be intact and the rest would be regenerated.
I don't play on the Xbox One... yet (still on the Xbox 360 for now) :D, but, I like this idea. It's original! (not like the infinite number of cries for infinite worlds) and it seems elegantly simple. I could see it as even a possibility (on a smaller scale) on the Xbox 360.
I've been suggesting similar for ages and I think this would be ideal if they can't expand world sizes. Something needs to be done to handle the limitations. Or whenever there is a change such as New biomes, then allow for a world expansion. Something to allow people to take advantage of new features.
Personally, instead of jumping into 1.9 development, I would like to see 4j attempt to address some of the console limitations such as this issue. The OPs suggestion is ideal if there is no plan for a world expansion.
Time to step back and look at what they have put out and see what everyone's complaints are and what possible solutions will work within the limitations on the consoles.
The ability to reset maps (and by maps, I mean 1000 x 1000 portions of your world) would be awesome. I've put a ridiculous amount of time and work into my save. I KNEW I should've left areas of it unexplored, but I wanted to find all my villages (and build roads to them).