There's never a final lens purchase... unless you count the inevitable final threshold, which I hope isn't the case. 😃 We always keep telling that we're done purchasing lenses, and at times, we really are... until we aren't. 🙂
Case in point: I'm seriously consider giving up all of my Canon gear (minus the 70-200 and probably the 16-35 which are two of my favourite lenses, and hold nostalgic value in addition to practical one) and going full Nikon / Sony lenses. That after telling my own self perhaps half a year ago that I'm all set with gears. 😃
OTT... the Nikon 28/1.8 seems like a fine lens, and I can only commend the intention to get rid of old AF-D fare, even if you're not getting mirrorless. The AF-S lenses just seem so much nicer in every respect, at least from reading the reviews here. Guess I was already fed up with screw-driven AF back in my (short) Minolta period 20 years ago. 🙂