The 3DS has managed throughout its lifespam to stay ahead of its direct competitor, the PS VIta, usually by a wide margain. However, with the NX coming soon as a possible replacement for both 3DS and WiiU means that the 3DS is going to stop getting as much support, and it will eventually be fully replaced by the NX. PS systems usually have a longer lifespam than its competitors, and the low costs Sony has on the Vita (they don't produce anything major anymore, and they sell a steady 40k units weekly plus PS+ and memory cards) could mean that, at some point, the Vita may sell more than the 3DS.
Now, I know that the release of the NX will mean a drop of Vita's sales too, but it will affect more the 3DS, due to being replaced by a direct successor, while the Vita will probably be the last fully dedicated handheld Sony ever produces and it can cling to the success of the PS4. Support of the Vita will be decent, at least in Europe and Japan, and the PSTV could be really cheap to make and manufacture in the long run.
How long will it take the Vita to pass the 3DS on weekly sales? Or will the Vita be fully discontinued before the 3DS?
EDIT: I'm not askingwhen the Vita will outsell the 3DS in total. The Vita won't be around that much time to sell +40m units. I'm asking when do you think when the Vita will beat the 3DS in weekly sales. Just like the Wii and the PS3, the Wii has outsold the PS3, but weekly now the PS3 sells more than the Wii.
You know it deserves the GOTY.