Amy,
While I would love to have a magic ball (seems like something Disney should be able to issue us, doesn't it?), I have no way of knowing what will, and won't be open by this fall. So let's be clear that what I say here is just my opinion.
When I peek over the top of the construction walls (riding Dumbo makes for a great view of the proceedings), you can see all the activity, especially around the Beast’s castle. I would expect that you will hear is that starting in the late spring the general area will open, largely around character meet-and-greets. Then as the summer proceeds the restaurants and attractions will start to open. If I had to guess, by November most all but a few attractions will be up and running.
What I would recommend is that you stay tuned to the
Disney Parks Blog. They are going to be a fun, official, and reliable place to read releases about the expansion.
And of course you can keep asking me questions too! When I hear more I will let you know!
Have a magical vacation!