When comparijng how novel the F-35 is against the 4.5 competition one has to take into account that the programme faces a 7-year delay (and counting). If the F-35 had been on time, then the SH would surely be obsolete by now. But it wasn't, and the SH/Growler now sport high-speed fibre-optic network, APG-79 AESA radar etc. While LM has to put enormous resources in trying to make an unproven plastic airframe carrier-capable, Boeing can focus on avionics, human interface, optical systems etc, that can be supplied by the same companies that deliver to F-35.
So thanks to F-35 misplanning, there is still a serious lease of life in SH. I would guess for at least 20 years, probably 30.