That's fine ... but as this is the "CTS Performance Mods" forum, I'm not sure what other content you'd expect to find discussed here?
Even a mod as simple as putting on a custom airbox has been known to void people's warranties when a dealer decided to be difficult. Really, your options come down to modifying NOTHING, or accepting some risk of hassle/problems with potential future warranty claims. (I mean, even if you tint your rear window, someone at a dealership could claim that voided your warranty on your rear defroster. If you put in a new radio, they could void a warranty claim on a defective door speaker in the future.) Heck, you could theoretically have some idiot mechanic try to void a claim on the AWD system if you used different tires than OEM, claiming it " changed the dynamics of the system".
For whatever it's worth, Trifecta claims they can apply some sort of "stealth mode" over the top of their tune after they reflash it, which hides it so the system will appear to be stock when checked. (Their software prompts, asking if you'd like to do that, after a reflash.) Does it really work? I don't know... I'm not the guy who designed it, but he DID work for Microsoft as a software developer for a living before starting Trifecta and doing custom tunes. So he may know a thing or two about that stuff?