Patch 2.3 launched relatively recently, 2.3.2 is on the PTR, and 2.4 is presumably pretty far from PTR still. As it turns out, that is expected to be about it in the way of pre-Wrath patches, according to Eyonix. 2.4 will introduce the Sunwell Plateau, an outdoor zone, including a 5-man dungeon and a 25-man raid at a harder-than-T6 difficulty level. There will probably be the now-usual assortment of class balance changes, new crafted items, and new daily quests as well, and being an outdoor zone, Sunwell Plateau will probably have some regular quests and a faction of its own as well.

Does the fact that there's no patch 2.5 planned mean anything about how close Wrath is? I'd say there's probably not much connection. If Blizzard knew that it was going to be, say, a year before the expansion, then yeah, they'd probably plan for another content patch. But seeing as how Eyonix saw fit to add "Time will tell, however" on to his post, I'd say we can't infer much more than that they don't expect the expansion to take a ridiculously long time. My prediction is next March, because that's when my birthday is and it'd be a nice present.