As easyjet have not yet released the S07 schedule it is hard to make a direct comparison,if you are looking for the best deal its all about timing,Jet2 have already published next years so the best fares are on offer now,however by the time easyjet publishes its fares around Dec/Jan all the cheap seats on jet2 will have been snapped up in which case it will be cheaper to book with easyjet,once they've all been taken you may find another carrier releasing its schedule and so on.
With regard to new routes there are a number of considerations,firstly do you dump a tried and tested route in favour of an untested one? The costs involved of starting new routes are pretty significant,advertising,new airport start up costs etc.Airlines will therefore consolidate routes they currently fly because they know what works and what doesn't.Bearing in mind the route network out of Newcastle now compared to 5 years ago its still pretty impressive.