This morning, Jet2 have released a statement regarding NBE for Summer 2016 on their website:
Jet2 stop selling flights and holidays to Tunisia
Jet2.com and Jet2holidays has stopped selling flights and holidays to Tunisia for the remainder of this year and summer 2016. The article states that instead, the airline has added more flights and holidays to their most popular holiday destinations.
With this and next summer no longer on sale, I suspect it'll be a considerable amount of time until (if) we see NBE back on the the Jet2 destination map again.