Bethesda could be releasing a 30 hour DLC if the trademark and the patents front are anything to go by.
Skyrim DLC: Redguard & Thalmor tipped coming before a Skyrim 6
According to the folks over at OXM, the next DLCs for Skyrim could have focus on Redguard, these are the warriors with skill that came from Hammerfell. The parent company of Bethesda, Zenimax have trademarked the term “Redguard” in the category of downloadable computer game software offered through the internet and wireless devices. They did this in March of 2011, but have not filed a Statement of Use.
Over the months they filed to extend the trademark, repeatedly, the most recent being in August of 2012. The trademark will expire in February of 2013, unless of course they file for an extension once again. Next generation hardware is expected to be released this year at the E3, or around it. So this could mean that it would be unwise to bring out a new Skyrim game yet, hence a couple more DLC packs.
Of course this is not the first Redguard focused title for Elder Scrolls that Bethesda has put together. They did release a 3rd person spin-off, the Elder Scrolls Adventures: Redguard, back in 1998.
On a side note, there were already rumors of another DLC coming to Skyrim based on the Thalmor. A fight with them always seemed inevitable. If so that would mean 5 DLC altogether for the current Skyrim game before we could see a Skyrim 6 (Xbox 720 & PS4 anyone?). The number ‘5’ does tie in well with past Skyrim games as they too saw 5 DLCs before sequels were announced.