Short answer: No.
Long Answer: No because the mod is still rather early in development. The plan, as far as i know is to add the solar system, as planets and moons into the game. That means it is unlikely that you will be able to have other worlds. HOWEVER: At some point the creator wants to produce a API that will help in creating new worlds which you might be able to use. That might still be a while though.
If you want to play with several worlds i would either use Mystcraft, or try to install Bukkit and use plugins like Multiverse, which is what the private server i play on has done in Tekkit Classic. I'm sure you can find this or a similar plugin for the new Minecraft version.
Still at this point the answer is no.