that's a good question, but even though there is not yet a software update for the XV6800, it is the same type of model, so i also dunno the risks behind using another Titan ROM Upgrade after unlocking the SPL. i too have read about the Alltel ROM being installed on the Mogul, but as i said in a bit of a different way earlier, i can't possibly tell you if the Sprint ROMs work on it, but you could definately ask about the Alltel ROM with the 1.40 radio (vs. the XV6800's default 1.30 and Sprint's 1.32 radios). here's a link to check for software updates for the XV6800 below...
http://www.htcamerica.net/support/default.html
funny thing about this is that the XV6800 is nowhere to be found, but you could in fact keep checking support and products for it.
glad to help anytime bro.