Nintendo was toying with 3G for 3DS (Iwata even talked about it publicly over a year ago), but the advantages (always online) didn't seem to outweigh the drawbacks (subscription, latency, battery drain) from their perspective. I think SpotPass is a bit of a middleground for what they wanted out of 3G.
Not all NGP models will be 3G capable either.
I do sort of see 3G (or hopefully 4G) being one of the components built into a 3DS refresh in 2 years or so. Hopefully OLED as well, since that should help bump up the battery life.







