As flight only companies like XL and freedom flights are curtailing their operations at NCL for next winter and possibly even next summer there is certainly a gap in the market, where Jet2 could pick up so the possibility of LS 757's operating to LPA, PFO and SSH is quite likely. Freedom/XL have had a fairly substantial winter programme this current winter season, using FJE to LPA, TFS, ACE, PFO, SSH and adhoc's to FUE for the holiday seasons. Indeed extra flights were added during busy periods, but obviously it was not profitable for these companies, hence they are not operating next winter, therefore it leaves potential for Jet2.
I also believe that YYZ is a possibility, the GSM service this summer is not exactly ideal, operating via MAN some weeks and direct others. YYZ could be served by a 757 a couple of days per week, though are Jet2's 757 a/c suitable for such long flights, in range yes, but what about pax comfort? I think the likes of NYC would be better served by a so called 'legacy' carrier with the option of upgraded service and connections throughout the US.