I suppose anything is possible, but I don't think it is very likely.
Yes, American audiences don't seem to love the 3DS as much as the DS, but the Vita is doing so poorly in sales I can't imagine it will leapfrog the 3DS. Both will probably lose sales in North America, but Vita will lose more.
A new Zelda game and some 3DS Pokemon games will keep 3DS going strong in the years to come.










