Let me peer into my magic 8 ball ;-) Seriously though, I bought the retina iPad 3 and six months later the 4 came out. Ugh! Almost seems like they're putting the iPad Airs on a two-year cycle now though, since it didn't get an update this year. I'd guess next fall Sept/Oct.
The big question is whether or not they'll hold the Pencil capability only on the "Pro" models or make it available for everyone. I'm pretty sure I'll keep my Pro through next year since the screen size is gorgeous for drawing at home, but I'd leap on next year's Air as well if it would also support the Pencil.
Lol. Well shoot. But I would agree, if it gets pencil support I'll grab it ASAP. If not, I'll stick with the 2.