It also requires a monster rig to run smoothly at highest graphics. I'm not talking "best thing you can find at a store", either. (or at least, that's how it was when it first came out in 2007.)
This would kill DF for me, and probably every other player out there. Permanently.
Even if my computer could handle it... Like other people have already said, there's just no way to get the detail Toady puts into DF into this kind of engine. I'd prefer DF as it is over Skyrim graphics.
Skyrim appears to be a particularly poor example, as it sounds like its engine is an even worse combination of dubious hacks than average. There's a couple of different points in here however.
Few current games do a really good job of handling wide ranges of rendering power. They may have the ability to crudely adjust distance cutoffs or texture sizes, but it's all the same engine with a few tunable parameters. One of the more interesting is Stardock's "Elemental: Fallen Enchantress"; it has two fundamentally different rendering modes, the default 3D and what it calls "cloth map" mode. The user can set at what zoom level the game switches between the two modes, and even set a config option to run in cloth map only mode, so the game can be played on a netbook (and perhaps eventually, a tablet or smartphone) without all the rendering overhead at all.
Given the decade or so we expect DF to take, it's not unreasonable to posit a multi-staged modular interface system:
* 2D pseudo-ASCII
* 2D graphical tiles
* pseudo-3D isometric tiles & sprites (Falcon's Eye or Stonesense style)
* 2D / 3D optimized hybrids (upcoming Shadowrun Returns uses a version of this. In a DF interpretation for instance, the engine could create a fortress dwarf from a combination of procedurally chosen 3D models and textures, then pre-render / "bake" a set of (2D) sprite animations from it that could be cached and rendered far faster in play. Original Wolfenstein 3D had a version of this, where room objects were really only 2D (basically like a cardboard cutout that always was rotated to face the player).)
* Simplified 3D; late PS2 or early PS3 grade 3D or older MMO equivalent, with a comparatively low poly count and texture size, but adequate to see what is going on. WoW-grade graphics would fall under here.
* Early 2010s MMO grade 3D; Aion or SWTOR characters probably have enough configuration options that an analogous engine could handle the variance amongst dwarves, for instance. Skyrim, Dragon Age, Crysis, etc. fall into the same very general category. By the time DF reaches much closer to finished, this sort of rendering at reasonable resolutions should be practical on fairly inexpensive devices. With procedural generation of the vast majority of the models, the storage space isn't all that large (although possibly still a separate download), and in any given fort only a small fraction would need to be loaded.
* Late 2010s / early 2020s grade "photorealistic" 3D: I would guess that Bay 12 would stop short of this, but might have hooks for those wanting to do up their own high-res models, or render existing ones in a more complex fashion. (For instance, at least one previous-gen MMORPG created their models and textures at a fairly high detail level, and then simplified them for device rendering; if you knew how, you could extract the actual models and textures, load them into an external 3D graphics program, and render them at a far higher quality and resolution than the game ever used interactively.)
One could posit having device-specific configuration files that specified the highest and lowest level you wanted to enable, and changing amongst the enabled levels with a hotkey, depending on your current desire for quality versus speed. Perhaps on your tablet you play in isometric tile mode normally, but drop to 2D top-down tiles when you want to pass the next month quickly, or crank up to simple 3D when you're trying to arrange some difficult mine-cart tracks while paused. On your gaming desktop, perhaps you play in 2010s 3D normally, dropping down to simplified 3D to speed megaproject construction, or up to 2020s 3D to admire a particularly cool scene and get a screenshot for the forums.