Dumb question, but will this affect the collections at other places; so, for example, will some paintings from the Orsay or Marmottan be moved here? Since I've seen Orsay and Marmottan, I'm wondering if the Orangerie will be more of the same, or new paintings. Still, it's exciting that Orangerie will be finally open.

JoeTro, it's not a dumb question. The musee de l'Orangerie has always had its own collection. I don't know what they did with those artworks over the years, whether they were displayed elsewhere, travelled in exhibitions, etc. (I did see at least one in a Modigliani retrospective.) But prior to the renovation closing the museum, they were only at the Orangerie. The Monet Nympheas (waterlilies) are set in their own oval-shaped rooms so that you're surrounded by them; the Guillaume collection of other Impressionist art is also very good.

Check out the museum's website. Even if you don't read French, you can click on the links to see some of the artworks.
http://www.musee-orangerie.fr/