Must say I'll be very surprised if the 352 and 355 see out beyond March 2024, the 352 in particular. There's very limited reason to use them unless you only travel Monday to Friday day times when Stagecoach are covering them with a more frequent service and an evening / Sunday service with cheaper fares to boot.
Even the 353, I wouldn't be surprised if it's a Killingworth to North Shields only service aswell for similar reasons on the Northern end of the route, with the 19 the same frequency and quicker for Cramlington to North Shields / Cobalt passengers.
RE: Go North East September 2023 changes