Could it be happening!? All it took was a government shutdown to convince Valve to take what looks to be the next step towards Half-Life 3. As spotted by NeoGAF, Valve has registered Half-Life 3 with Europe's trademarks office, the OHIM.
Upon visiting the actual European trademark office website and looking up the trademark (#012180394), you can clearly see it's legit. Valve apparently registered for the trademark on September 29, 2013, and it's currently listed as "Computer game software; Electronic game software; Downloadable computer game software via a global computer network and wireless devices; Video game software."
While the trademark appears to be official, Valve's actual motivation remains in question. Is Valve actually taking the next step in developing Half-Life 3 or are they merely trying to protect their IP?
Things certainly just got a whole lot more interesting!