Converting a 3.6 style to a 3.8 compatible style isn't THAT hard though, the main pitfalls are basiclly the member profile and the parts of vBulletin (like the social groups) that uses a tableless way to style the page that might create some minor issues after an upgrade if the style and css properties in the control panel is heavily customized.

Even for this style, it shouldn't be much more than a few hours of work, even less if people work together and then some testing and done.