When Minecraft 1.2 comes, we will probably expand the borders so that jungles etc can be included in our worlds. The Nether may be pruned then expanded at that time. At the moment, we are letting you wander where you like but giving you no map. We may later decide to set borders and give you a map.
And yes, getting portals to go to the right places is always an issue. That is why we counsel against building them in the Nether (just in the overworld). However, sometimes that may be necessary. If you are not sure how to map Nether portals to overworld portals, then ask on the forum. Better to be safe than sorry.
Last edited by Sorontar; 16th February 2012 at 09:48 AM.