At level 46 you can enter Plane of Tranquility, Plane of Justice, Plane of Innovation, Plane of Disease, and Plane of Nightmare.
The reason it gets confusing after that is that there used to be a required progression of flags, etc, as denoted by
this link. HOWEVER nowadays to get access to some of the planes all you have to do these days is be level 51, 56 or 62(?). Gaining access via levels does not move you along towards the elemental planes but it does open up new exp zones.
Hope that helps a little. For the next few levels I'd stay in Plane of Justice anyway. Most of the planar zones are pretty rough at 46.
Oh, heh. Forgot to mention other planes. The old world planes (Hate, Fear and Sky) are totally accessible at level 46, but don't go alone. In fact don't go with a raid until you've secured 46 with a two-death margin.