Update: Microsoft officials sent overnight the following clarification:" Microsoft Advertising is not changing branding. What was called the 'Search Alliance' is now the Yahoo Bing Network. AdCenter is being rebranded to Bing Ads."
Yahoo Bing Network looks to be the new name for the combined Yahoo and Microsoft core search sites, which Microsoft is touting as accounting for 30 percent search share in the U.S. Microsoft (and Yahoo) also are highlighting as part of the rebranding that it's not just Yahoo that is powered by Bing. On the new Facebook page for the rebranded advertising network, the pair emphasized that the "Yahoo! Bing Network is the combined search advertising marketplace made up of Yahoo!, Bing, and partner sites," like Facebook, Amazon, Monster, WebMD, CNBC, and Viacom, plus networks like The Wall Street Journal Digital Network.
"The robust Yahoo! Bing Network reaches 151 million searchers in the U.S. who are likely to spend 124% more than the average searcher, and likely to spend 5% more than Google searchers in the U.S. That also means you can reach 46 million unique searchers in the U.S. who aren’t using Google, claimed Microsoft on the new Yahoo Bing Network About page. "A similar result holds true worldwide, with 489 million unique searchers, 92 million of whom do not use Google; and worldwide the Yahoo! Bing Network represents an audience who is likely to spend 124% more than the average searcher and 78% more than Google searchers worldwide."
I asked Microsoft officials for comment on the company's rebranding plans beyond the information that is now available online. No word back so far.
Update 2 (from September 9): It looks like the move is now an officially acknowledged done deal. Microsoft posted to the Bing Ads Community blog site an announcement of the rebranding. "We’re pleased to announce Bing Ads as the new name for Microsoft Advertising adCenter, the tool you use to manage search ads on the Yahoo! Bing Network."