|MadSci Network: Astronomy|
The simple answer is that another solar system won't directly form around the Sun---the planets are here to stay until the Sun ends its life, which should happen in another 6,000 million years or so. Just before that happens the Sun will swell up and become a large, cooler star known as a red giant---and might even swallow the Earth as it does so.
The interesting thing to ask is where the material that forms the solar system comes from. In the big bang, which began the universe, only a few elements were created---all that existed was hydrogen and helium. But you and I and the world around us are made of much more---life, for example, is based on carbon. Every single atom of every single one of these heavy elements came from deep inside a star that reached the end of its life and exploded when it ran out of fuel. So, as Carl Sagan often said "We are stardust". Amazing thought, isn't it?
Finally, you ask if we're the 2nd or more Earth in our galaxy. Well, there may not be more Earths here, but we're becomming increasingly sure that there are plenty more Earth-sized planets out there. Ten years ago, the only planets we knew about orbited our Sun. Now we know of over 50 around more than 20 stars! We can't detect planets the size of Earth yet---but watch this space!
Try the links in the MadSci Library for more information on Astronomy.