Yes, purchase a wheel that has the braking surface on the rim for your v-brakes and a hub with the bolt pattern for a disc brake.
http://www.jensonusa.com/store/produ...+Wheelset.aspx
You may want nicer hubs... but you get the point,
They're(discs and v-brake hubs) all spaced 135mm and 100mm. Just make sure your fork doesn't have strange stuff that might hit the disc brake bolt holes.