This one is sort-of official: Microsoft has confirmed via the Nokia France page on Facebook that it will continue to use the Lumia brand for its smart phones going forward. So the Nokia Lumia brand will be replaced by Microsoft Lumia.
"In the coming days, you will receive a message from Facebook on the renaming of this page," a translated version of the post on the Nokia France page reads. "We are about to become 'Microsoft Lumia'! Stay tuned to learn more soon."
OK, so this one isn't surprising in any way, shape or form. And it was telegraphed pretty clearly by Microsoft, which has, among other things, started using the Lumia brand prominently in its advertising while dropping the Nokia bit (which it can legally use for basically all of eternity if it wants).
More controversial, perhaps, is that Microsoft and its partners have been not-so-subtly dropping the "Phone" part of the "Windows Phone" brand in advertising and online promotions as well. This is leading some to believe—quite reasonably—that with Windows 10, Microsoft will simply use Windows as the overarching brand. So you won't be using a Windows Phone handset. You'll be using a Windows phone, with a small "p".