We can now confirm that the "Half-Life 3" trademark has been removed from the Trademarks and Design Registration Office of the European Union (OHIM) website. The entrant appears to have disappeared entirely after only being listed on the website database for little over a week, allowing us to identify that the trademark's listing was more than likely a hoax intended to generate fake buzz for a game which is unlikely to appear for several years. Returning readers may remember when we had discussed how the "Half-Life 3" listing was previously never officially checked or authenticated before its removal.
On October 2nd 2013, a brand new trademark filing appeared on the same site, this time for "Portal 3", which is listed under the trademark number of "012190286". While this new filing should almost definitely be taken with a rather large pinch of salt, we can confirm that the "Portal 3" listing appears to have been appropriately examined by OHIM, unlike the previously listed "Half-Life 3" trademark. Thanks to the recent sneak peak into Valve's Jira account, we can confirm that there is currently no "Portal 3" development team within the company, highlighting that this brand new listing is also very likely a hoax of some kind, regardless of whether or not it has been officially examined. We'll keep you posted if and when we learn more.
There has been some talk today on the Neogaf forums surrounding Valve's registration of the name "Half-Life 3" as a trademark in Europe on September 29th. No such similar trademark exists in the US Patents and Trademark office. While it is tempting to get excited about such a development, it is worth noting that it is fairly common place for a company to hold onto numerical trademarks and web addresses far ahead of any potential future release in order to prevent complications further down the line. The trademark has yet to be appropriately examined and approved, as shown below.
A quick search of the US Patents and Trademark office shows that Valve already own such names for potential products in the future, including Dota 3, and of course Valve have regularly updated their ownership of the www.half-life3.com domain over the last few years. Please remember that the existence of a trademark such as this has very little to do with the development of any game title, as we imagine this kind of trademark is submitted simply to protect intellectual property, regardless of whether or not a company will ever use said trademark. A recent example of this comes directly from publisher Electronic Arts, who registered domain names for the Battlefield series as far ahead as Battlefield 20!
Until such time as there is an official announcement or direct reference to the upcoming release of a new game or series, it is best to consider all such discoveries as nothing more than rumours.