According to the official announcement on August 14, 2015, "The Jungle Skipper Canteen is currently under construction and will open its doors in late 2015."
It would seem like good business to be open for the holiday crowds of the latter half of December. And it would seem like good operational practice to be open a few weeks before the big crowds arrive, to get everything running smoothly.
WDW is good at project management. (Sometimes things at WDW take a long time, but the long project calendar is planned that way.) Even the best project plan can have unexpected delays, but building out a restaurant is not rocket science. It's not like an attraction with unproven, cutting edge technology. A good project plan for a restaurant should not slip.
My guess is that the target opening is around December 1.
I could be wrong.