The base has been deffered to 2017 now.
Reason being that vueling have had some really bad OTP issues this summer, and therefore will not open any new bases in 2016 to try and recover some reputation, by bolstering the current bases. This is not a slight on MAN, it's a network wide issue, and that's where the priority lies at the moment.
In terms of MAN, they have said new routes from current bases will still happen, notably Palma, Ibiza, Florence, Seville and Alicante, and currently Barcelona in August 2016 will see a daily schedule with July being 6 weekly (already bookable on their website).
Rome FCO was also to be a new route, but, Rome has its own issue to deal with at the moment. All new routes will be 2-3 weekly at most. Barcelona may still get its 10 weekly flights, as further adjustments are due.
The new routes should be available to book from about January, with an April/may start.