Content compared with D3?

How much playable content will PoE have?

Also will there be in game trading of any kind?

There are 2 acts played through for each of 4 difficulties currently, which could be anywhere from days to weeks of play time depending on your speed. Compared to D3's beta, there is far more available content in the PoE beta.

There will be robust trading features in the future, ranging from the standard player-to-player interface to forum trade features.

This is all stuff that is currently being worked on for PoE

http://www.pathofexile.com/forum/view-forum/253

I believe I also read somewhere that PoE is planned to have a 10 year life span meaning they will keep adding content for 10 years after release; but I suppose only time and money will tell on that one.

It currently has 2 acts, there will be 3 at open beta, 4 acts at release, and more will come after.

Currently you can only trade by partying up and dropping stuff, but trading interface and other features are in the works.