At the 2003 Con, HT himself said that he had already created searchlights in AH2. IIRC, however, he'd just done them as an experiement for something else so set them aside to work on more important matters before he'd developed them far enough to track planes. Apparently, they just waved around randomly.
But everybody oo'd and ahh'd at the Con, so I figure eventually we'll see them. However, to make that worthwhile, night's got to stop being a joke. When folks can avoid it by jacking up their vidcard gamma outside the game's gamma control, there's no real point in doing night stuff IMHO.