some facts make this out to be quite possibly the super rumored riders of hammerfell
the reason i say this and speculate it is:

1. it was trademarked in post production phase of the vanilla skyrim
as skyrim was released in fall 0f 2011 and most developers are already creating dlc in that stage

so far the only trademarks to use the same font have been dlc of skyrim dawnguard, hearthfire and now dragonborn all use the same font where as fos ro dah used a entirely different font

Redguard was trademarked as computer software for games and consoles as downloadable content

ill post link to the trademark site here where you all can tell what you think also

I was one of the first to specualte that dragonborn was acctually a dlc when others thought it was just a term trademark

so here i am doing the same again with Redguard
http://tess2.uspto.gov/bin/gate.exe?f=search&state=4004:7ipeq9.1.1
search zenimax and look at previously released dlc and info in the filling and then look at redguard

Maybe they are protecting the game name of The Elder Scrolls Adventures: Redguard.

The first big expansion pack?

Dawnguard was kind of big (it's often underestimated IMO, do people always expect something to be the size of Shivering isles?)
and Dragonborn will definitely be big too.

But I doubt Hammerfell will be an expansion.

could be but why use the same font? and there was speculation of a hammerfell dlc shortly after and todd howard did say that they thought it would be nice to maybe see hamerfell in a dlc kinda like a hint if you may

however i may be wrong but there was talk of large dlc/expantions and i kinda dont think that anything up to this point is what they are considering to be large dlc chunks due to the way they priced them at 1600 msp and shivering isles was 2600 i believe if i am incorrect then please excuse me on this speculations

Might be another free release from the past like Arena and Daggerfall.

Todd never said anything about revisiting Hammerfell but he did say he wanted to see Daggerfall again.

If anything, a Stros M'kai expansion would be sweet!

can anyone comment on why the previous dlc of skyrim all use the same font as well as redguard but other elder scrolls fonts are different to me it seems only dlc share the same fonts

Makes Redguard more likley for TES-Online since none of the other Skyrim DLC's have or need this.

Dragonborn will be the first big expansion. But it would be nice to visit Stros M'Kai.

This would be even nicer

good catch
http://www.gamesas.com/user/412936-rhomphaia/ I didnt see that