Remember, a "Refurb" is not considered a "Layover" such as HMH and IASW Holiday.
I wouldn't think they would be doing any "Refurbs" until next year at least, after the holiday and the initial 50th celebration stuff kind of dies down a bit.
The 50th celebration is 18 months, I don't think they will be able to have no refurbishments whatsoever during that time.
I think the rides that will be safe from Refurb during that time though would be IASW (except for holiday), HM (except for holiday), DLRR, Splash Mtn, Space Mtn, Indy, Buzz and Jungle Cruise since all have received rather extensive rehabs, or are new.
I would still expect to see the typical Matterhorn, Pirates, Big Thunder, Peter Pan, and FL Dark ride rehabs during the 50th. Not sure if it's possible to have those rides open for 18+ months without any downtime. Mostly due to their age.