I still don't understand how no one saw this coming way back when the Caballeros invaded GFT.
HALT! Armchair Imagineering time!
In no way does this suggest the blaspheme of replacing the Norway pavilion with a fictional Arendale. Disney would never do this. The integrity of the World Showcase would be completely compromised.
Disney will pay for an update to the pavilion with money in advance from Norway or from money in the long run by injecting Frozen into it. That's it.
My Speculation
Enter the Frozen girls. Wether you like them or not, they revitalized Disney in a lot of ways. They were the first Princess movie to hit big B.O. numbers in a long time, and the M&G's drive Frozen fans to the parks in droves.
Walt Disney Animation Studios Box Office Records
#1 Frozen $400,738,009
#2 Tangled $200,821,936
They see the kind of draw these girls can pull, even with a poorly thrown together M&G area in the Norway pavilion. So updating Maelstrom along the lines of GFT or Living Seas (injection of characters, or characterization) using the girls and their amazing draw power seems like an even better idea than Norway funding it in the first place.
Of course with any amount of significant change, there will inevitably be haters. I think of an old grandpa shaking his fists at these new fangled smart phones! "Gimme an old rotary dial for goodness sake! They never should have changed it from the good old days!"