There's nothing that military loves more than modernizations, basically "we can make old rustbucked kill enemy's new thingy for a fraction of its price" (for example, look how extensively tanks are being upgraded instead of replaced). It's reasonable that sensors would be quickly replaced if they became outdated, along with targeting systems, so they aren't completely left in the dust.
@PCCL well, for one thing, it won't be aliens if I recall correctly. Alex said there wouldn't be any. So I guess DoM's experiments gone wrong.