Are there already Dell XPS models with anti-glare touchscreen?!

Why would it not be possible to develop matte touchscreens? There are already 3th party companies who make matte screen protectors for the XPS but these are difficult to bring on. If Dell could include such a matte protector in the manufacturing process it would be a more integrated solution.

Why would  that not be possible??

First, a little background on touchscreens.  Most modern touchscreens are capacitive, which means they detect touch by sensing a change in electrical current somewhere on a grid that exists over the display.  Your skin conducts enough electricity to create this change, and glass ALSO conducts electricity, which is why touchscreens are overlaid with edge-to-edge glass.  (This is also why touchscreens typically DON'T work when you're wearing gloves unless the gloves themselves are specifically designed with a conductive material at the fingertips.)  There are also older "resistive" touchscreens that detect touch by having you physically deflect the display when you touch it, and the location is identified by having a grid mounted underneath the display that identifies where the display touched it when it was depressed, but those are less commonly used today.

If you've ever looked at the touch and non-touch versions of the same laptop model, you'll notice that the touch version has edge-to-edge glass, including over the display bezel, whereas the non-touch version has nothing covering the display, and the bezel creates a "ridge" around the display itself.  I suppose theoretically it may be possible to have some sort of touch digitzer in the stack of a matte display, but it's possible that this would create more headaches than it's worth.  For example, another side benefit of edge-to-edge glass is that it makes the display easy to clean when the inevitable smudges crop up from touchscreen use.  With an exposed matte display, users would have to take much more care when cleaning it, and some users inevitably wouldn't and would then complain that the vendor made a low-quality product when they caused damage with harsh chemicals, rough application, etc.  And then there's simply the marketing aspect.  Consumers interested in gimmicky features like touchscreens tend to prefer glossy displays because they make colors look vibrant.  Professionals that prefer matte displays for anti-glare benefits tend not to care about having a touchscreen.  There may simply not be enough of a market to justify this even if it would technically be feasible, which might explain why despite touchscreens having been on the market for 4+ years now, there are still no matte versions.

Dell doesn't make LCDs -- only a handful of very large manufacturers (Samsung, LG,  Sharp, AU Optronics, etc.)  do.  As the other post notes, the function of a touchscreen is at cross purpose with a matte covering - and I wouldn't want to have to clean a touchscreen with a matte finish on it (it's tough enough to keep a smooth surface clean).