“Already you can tell if a stealth craft is operating in an area, even if not quite good enough for a missile lock just yet, to give one example.”
You put you finger on (perhaps) the last redeeming advantage of stealth aircraft - the ability to prevent, or easily break, a missile lock. You don’t hear a lot of talk about it. But just look at the huge radars used in the Russian S-400 system. There are dozens of them. Some for long-range detection, some for tracking and some for targeting. Take away 1 or 2 critical radars and the entire network is severely degraded. And if you manage to vector fighters out to the stealth intruders they may as well be throwing rocks. As soon as they ‘lock-up’ a stealth target and fire, they won’t be able to move to the next target because the tiny radar dish inside the AAM is too small to get & maintain it’s own lock.
Less than you might think - the S300 and S400 can be datalinked in a virtual Very Large Array. This massively helps them detect stealth craft and the loss of one or two radars doesn’t degrade such a VVLA much.