Hopefully Jet2 will stick on the route.
They offer more baggage, and have now got a bit of a following at MAN. Ive also heard the flights are usually rammed full, so there should be room for 2. Also, this day has been coming for years, as Easyjet has threatened to serve MAN-TLV in the past, but Jet2 stuck with it.
There is also the fact that the MAN airport timetable shows Jet2 increasing to 4-5 weekly every year, and whilst it hasn't materialised, there is no smoke without fire. This means if Jet2 thought there could be 4 flights per week, the fact this number has now been reached means it could be sustainable.
But there is the other hand, where, history tells us, they don't like to share on Niche routes at MAN (Milan, Madrid, Istanbul to name 3).
I suppose only time will tell as I thought Budapest could suffer now Ryanair serve MAN-BUD too, but, Jet2 seem to have stuck it out with a daily flight.