the 3DS is selling fairly well actually, not sure all of the negativity around it. Its actually getting kind of old at this point for a hanhdled (what are we at, 5 years?) and its generally still outselling the Xone despite the Xone being much newer. and like you point out, the Xone being lowered under 300$ actually begins to put it in a muchhhh closer pricepoint to the 3DS, considering default 3DS's are close to like 200$ and special edition versions (which are constantly coming out and bought a lot) can go even higher
The Xone is not doing well. Its doing great in USA but terrible elsewhere. I would be shocked if it ever catches the 3DS, and that's even after considering the NX will be coming out next year and killing the 3DS's momentum. I just recognize that when Pokemon comes out this holiday season the 3DS is probably going to be selling like DOUBLE the hardware as the Xone for a few months.
Unless the updated Xone is some sort of miracle system with amazing specs I don't see it being able to stay in contention with the PS4 and I wouldn't be surprised if the Nintendo NX pops up and takes all of the attention for the 'second system' spot away from Microsoft and further pushes it down
