Probably a good idea. By then both will (probably) have come down in price so you'll be able to get them for less.
I mean it is about ten months away so they should have dropped in price by then. :)
(Sorry for not responding, I was out).
Well, I'd definitely get the 3DS XL. I have had both, I traded in my old 3DS for the XL, and I have to say it was a great decision.
The bigger screens are a lot better for playing games on. Plus, it comes with a 4GB SD card (I believe) and has improved battery life! So yes, get the XL! :D