http://oami.europa.eu/CTMOnline/RequestManager/en_DetailCTM_NoReg#
Go to that website and search Half Life. As of two days ago Valve filed a patent for Half Life 3. Apparently Valve will confirm shortly. If it's really HL3 I'm gonna cry.
EDIT: Source - http://www.polygon.com/2013/10/1/4791490/half-life-3-trademark-filed-in-europe
EDIT2: