Vita is close to 2m LTD in the US, while the 3DS is still below 15m, for that 10:1 to happen the Vita would need to stop selling at 2m (which is reasonabe :P) while the 3DS would have to sell over 5m.
Now, if the New 3DS actually manages to revitalize sales of the system in the US it might do it, however I think something in the likes of 7:1 or 8:1 is more realistic.














