I will be back on Minecraft pretty soon, about 3-4 weeks (hopefully).
I was thinking about having each world - both the new one and the old one - each loaded on the server every other month. For example, for June we will have the new world, in July the old world, etc.
That will allow us to build on a new world while still allowing us to relive the nostalgia of the old world.
I like the idea of a new world, as we can start from a clean slate, but I love the old world, especially for how "alive" it was.