Personally, I'd be very happy with a prequel or a sequel as long as it was done well, but if it were up to me I'd choose a prequel. I'd love to learn all the stories of the jinchuuriki - that'd make a great series! Naruto: Tales of the Jinchuuriki... of course, we might just end up learning their stories in Naruto Shippuden, but if we don't I'll be burning with curiosity.