They'll probably void anything they can directly relate a problem to. So, they'd prob void any suspension parts, which don't seem to be a problem, but ball joints(which tend to go out on these trucks) would definitely not be covered. When I had my first truck, I put a lift on it and took it to the dealer and they even told me that because of the bigger tires that my transmission wouldn't be covered anymore.... Not sure if they can relate it out that far but the whole law deal about the denial of warranty places the burden on you for proving that the lift did not cause the issue.
That all being said, my lift is being built by trevor at PMF as we speak. Haha