Gitmo will close.  But only because Obama wants to improve our image with the world.  But, what will they do with all those captured terrorists?

They will simply lock them up somewhere else.

They won't be tried in a civil court because the rules of law in civil court has greater requirements on rules of evidence etc.  And let's be realistic, they weren't captured by CSI Miami.  They were captured on the battle field.  Soldiers don't have time to take pictures, collect bullets, interview "witnesses" or any of those other required evidence components that would be required in a civil court. 

The terrorists aren't with a government per se.  They don't wear uniforms.  Some argue that since they operate outside the rules of the Geneva convention and are not therefore entitled to Geneva convention agreements on treatment.

Likely the US will find a "new home" for the detainees and then try them by military tribunal.  It won't be a complicated procedure.  The fact that the detainee will have been captured on the battle field or is a known terrorist (where evidence does exist to support the claim) will likely be enough to detain some indefinately.

If Obama lets some go and they turn around and attack America or her interests, Obama won't survive the political fallout.