As Bing have been saying for a while the new Bingbot is coming 1st OCtober according to post.
Name change
As of October 1st, you’ll start seeing the following user agent name in your server logs:
Mozilla/5.0 (compatible; bingbot/2.0 +http://www.bing.com/bingbot.htm)
The old HTTP header From field, currently seen as:
From: msnbot(at)microsoft.com
will be renamed to the following:
From: bingbot(at)microsoft.com