John Fredrick Parker
Donor
Trade is unlikely. To make interstellar trade worthwhile, you'd need to find a substance that can't be produced at home and is expensive and low-bulk enough to justify shipping it rather than finding a way to duplicate it. As of now, we know of no substance that exists in nearby star systems that doesn't exist in Sol system. This is not to say that we will never find one, but we currently know of no physical process that would make one system or another rich or poor in any given material.
The only trade I can see is Intellectual Trade, the sale of art and intellectual property by electromagnetic signals.
Actually, due to comparative advantage, the human race doesn't necessarily need to be better at or have more of something than the aliens to trade with them, and for us to dramatically accumulate (some of) their technology. As Coase says, if nothing stops people from trading, nothing will stop them from trading...