Bill Sweetman was at Aero India, and he noticed that the Zhuk-M1E proposed for Mig-29 upgrades has been treated with a bit of radar absorbent material (top picture).
This won’t make a plane invisible, but it will significantly reduce the RCS of an aircraft in the front aspect, so the rule of thumb, about 5m2 is likely no longer operative, particularly when juxtaposed with RAM coatings on the inlets, fan, or the installation of radar blocker screens, as was done with the F/A-18 E/F, though the environment in an engine inlet is rather more severe than that found under a radome.
You can see a similar application on the Have Glass II F-16s (bottom, the RAM is white).
Additionally, the move to AESA radars might provide some additional reductions.
This probably doesn’t reduce detection much, but it probably does increase the effectiveness of jamming relative, particularly with the necessarily (physics is a bitch) high frequency radars on air-to-air missile seekers.
Also, you may want to check out this PowerPoint (19.3M) for some perspectives.