brontodon

The zoom looks like it's probably a bit better-made than the similar Nikon 200-500mm zoom. I understand that the zooming control is easier to use than the Nikon and the lens goes 100mm longer. I suppose this justifies the higher price. (I do like the constant aperture feature of the Nikkor, though!)

MDI Mainer

According to this report, in November 2018 Tamron applied for a patent in Japan to develop a 150-600 mm FE lens, apparently by adapting the existing G2 design for mirrorless models. That approach, of course, would not enjoy the internal zoom feature of the new Sony, but would likely bring the cost down. For me, at least, the real issue would be autofocus compatibility with the myriad of e-mount bodies.

http://thenewcamera.com/tamron-patent-70-200mm-and-150-600mm-lens-for-mirrorless-mounts/

So an offering from them to compete with the new Sony zoom may be afoot. Can Sigma be far behind?

Anyone fluent in Japanese (and technical design terminology for lenses) might be able to do some further research here:

https://hi-lows-note.blog.so-net.ne.jp/2018-11-02

MDI Mainer

gwilliams6

Both these lenses will perform 20fps with the Sony A9. The A9's exclusive FF stacked sensor has the fastest readout of any FF mirrorless or FF DSLR camera on the market, and can perform 60 autofocus and 60 exposure calculations per second. No other current FF camera can do that, DSLR or Mirrorless. That coupled with fast linear motors (600mm f4 ), and direct drive motors (200-600mm f5.6-6.3) will allow these lenses to perform equal to and beyond the competition's best, whether 10fps on the A7III and A7RIII, or 20fps on the A9. .

And Sony Execs say these lenses are designed for cameras with even faster fps than the current A9. (hinting at a new, even faster fps A9II later this year, ahead of next year's Tokyo Olympic games) .

These were launched now to be ready for the games next year and pre-orders are already heavy around the world. Sony says that their similar 400mm f2.8 GM lens launched last year has sold double the units they anticipated, so there is certainly a market, even for the expensive 400mm f2.8 and 600mm f4.

Longtime Nikon shooter and Wildlife master Mark Smith has much to say here after trying them out:

Sony 600mm F4 - Sony 200-600 - A9 - First Impressions - Sports and Bird Photography
https://www.youtube.com/watch?v=ZQioD-nJelQ

Mark Smith's youtube channel where you can see how accomplished a wildlife shooter he is:
https://www.youtube.com/channel/UCyGYUrC2IvaHWoX6dwEsrMA

Full disclosure, yes I have pre-ordered the 200-600mm f5.6-6.3 and I have traded back in my excellent Sigma Contemporary 150-600mm f5-6.3 lens (Canon mount) which I used with the Sigma MC-11 adapter on my Sony cameras, A7RIII and A9.