So, I went into No-clip like the BAMF I am and travelled down this path.

So, if Im facing north east, that mountain is actually Red Mountain in Vvardenfell, which is apart of Morrowind! Red Mountain is located within the Middle of Vvardenfell, and can be seen on many other Tamriel maps, and in the game Morrowind. So, bethesda has made the landmass for Morrowind. The entirety of morrowind. Solstheim is there, the mainland is there, Vvardenfell is there. Its all there. Its scaled down slightly however, since the scaling in Morrowind, Skyrim, And Oblivion are all obscured towards each other. But its still very large.

The short answer to that titular question is that they already do, provided you have the right tools. One such gamer - a 19 year old Finnish fellow by the name of Jesse - does have the right tools, as he discover that without console commands it was possible to gain access to the landmass of almost all of the provinces of Tamriel, posting the results on his Tumblr . Jesse, like other Skyrim players before him, found that heading North East from Stendarrs Beacon lead to the discovery of a path between two huge mountains, which seemed too ornate and well designed to be without purpose.At the end of said path lay this gateway, built with a usually impenetrable invisible boundary.Personally I share Jesse's sentiment that the inclusion of this portal towards Morrowind seems strangely superfluous unless Bethesda have so-far veiled intentions. So I too may have done the same as him, given the opportunity: as he so eloquently puts it, he refused to accept the physical boundary...What he discovered was that beyond the limits of the game, the landmass remained populated with environmental features - trees, grass, rocks that sort of thing. And despite a gradual fade in quality, the textures remained for some distance beyond the gateway. Using some sleuth-like skills, and a remarkable dedication to the task, Jesse used his knowledge of Tamriel, and existing maps and visible reference points to plot out his likely position within the wider Elder Scrolls environment. And this is what he came up with...And once more, I'll leave it to Jesse to state the facts of his discovery...Advancing further, the fledgling Indiana Jones discovered landmasses that distinctly (though not entirely) resembled the other provinces of Tamriel, including Cyrodill, which he identified by comparing the two land-masses below. On the left of course is Cyrodill as it appeared in Oblivion, complete with the Imperial City and the right, blurrier image is of the equivalent area in Skyrim.I have to say good work to Jesse for the effort and the curiosity: hopefully this means that Bethesda are planning to use the land for DLC, but then it may simply be an exercise in pleasing the modders that they rely on to keep interest in the game well beyond the traditional realms. That second explanation would make sense, and I'm sure modders will be happy with the suggestion that they have been given what amounts to a huge blank cnavas to play with, but there is just something about the way that gateway is set-up that makes me think something else is on its way. And I would love it to be DLC. Problem is of course, Morrowind doesn't exist anymore, thanks to a volcano so even if Bethesda do choose to set some DLC there, there would have to be a major narrative development to accomodate it. Like some sort of mega-Balrog or Balrog army living in the volcano. just any Balrogs really. Holy shit, imagine that. As a final note, here's a whistle-stop 6 minute no clipping tour of the entire landmass, thanks to Youtube user Artdeux ... http://youtu.be/PlbA2qiXsf0 I salute you intrepid travellers one and all.