I think I'd still go for the 24-200 even if the Tamron 28-200 were available - simply because 24 != 28 !
I would of said the same thing a few years ago, but Samyang makes an excellent 18mm 2.8 AF lens that's no bigger than a Nikon 50mm 1.8 G lens. It makes a perfect companion to the 28-200mm. Those two lenses can cover a huge range for me with my Sony A9. I also have the excellent and compact Samyang 45mm 1.8 which gives me a very powerful 3 lens travel kit. Saying that, I still adore my Nikon brand F-mount lenses. I have an FT-Z adapter and I'm waiting to see how Z camera body prices look at the end of the year.