@Tsuchinoko
I went from a 2GB to a 32GB without problems. I just put my current card in my computer, did a exact copy of everything on it and then put that copy on the new SD card. My 3DS didn't have any problems recognizing the data (which it shouldn't since it was exactly the same only that the card had more memory.).
@RR529
That would be extremely weird. Launching a service like that and only allowing 1st party titles would be very stupid (but then again.. it's Nintendo..). They need to have at least 4-7 games available when they start doing this IMO. Having JUST NSMB.2 would suck.