Defeat the current threat before worrying about the next potential one.
The previous generation of aircraft had to descend to deliver the level of performance necessary to defeat or generate miss distance. I expect the current generation are more able to sustain altitude to do the same.
Add Jamming / Stealth etc and maybe the scenario is less relevant. There is a good video out there of an F16 evading multiple SAM launches during GW1. I am sure someone will have a link.
Adour