It depends. Due to its hybrid nature, there's no telling what sort of effect the NX will have on 3DS sales.
On one hand, yes, the release of a successor tends to adversely effect a console's sales.
But when you look at the actual release schedule, the NX seems to be more of a successor of the Wii U than 3DS. While Wii U software looks to be ending soon, we have high profile 3DS releases going well into next year.
So, will the NX be backwards compatible with 3DS software? Will the NX's launch cause Nintendo to stop supporting the 3DS with marketing? Will Nintendo continue to treat the 3DS as a viable platform after the NX is launched?
If Nintendo continues to market and support the 3DS through next year, ESPECIALLY if the NX isn't capable of playing 3DS software, I certainly think the 3DS will be able to hit 70 million lifetime, unless the system completely collapses in sales this holiday season.
The 3DS was already just short of 60 million at the end of June, and given it's increased sales over the summer, it's probably well past 61 million now. With the release of a new pokemon and a very cheap 2DS option, we 3DS should at least match 2015's 3.6 million for the holiday quarter, bringing us fairly close to 65 million. It wouldn't be too much of a feat for 3DS to sell a little over 5 million next year, providing the favorable conditions I mentioned are met.







