It's your call on whether you want to wait for N3DS support from Gateway or not. It's definitely coming, but nobody knows when exactly.
If you get an N3DS, do not update its firmware. Every region you can buy it from now has 8.1 - 9.0, I believe, and you want to be on firmware 9.2 or lower. The newest release from Nintendo is 9.4, and that update is not compatible with Gateway.