The "SF" line is highly marketed to the birding community. Although we have a small near cult following for the Swaro 10X50 here on the Forum (saying this as a fellow owner), I doubt that a 50mm binocular has a strong appeal to most birders. Zeiss may eventually come out with a flat field 50mm, but I would not be surprised that it is not an SF.....
...Zeiss has the 54mm HT as mentioned, and I would expect a 32mm SF at some point.
I have found Zeiss does not need a 50mm SF, the 42mm does things very well.
Lately, the big noise has softened over some of those with the Swarovski 10x50 SV, who have found some nice advantages with the SF.
I predicted that.

....
Would you buy one if they produce it ?
I've got an idea that a 10X50 SF would show a little more CA than the 10X42 SF, just a thought based on owning both the 10X50 and 10X42 SV, but I may be full of hooey on that since I can't see them now to be sure. Open that purse and get the closeout 10X now before they're gone, you'll be glad you did, a change in color and new eyecups that retrofit the gray model anyway aren't worth $1000 extra. The gray 10 I have now seems like a mature product compared to my earlier one, a beautiful focus action, and a beautiful image, the eyecups may not be great but I leave them down so I can't say. It seems also that putting heavier objectives out front would require a redoing of the amazing balance of the 42. I'm glad you asked the question though, it's interesting and the binocular might be fantastic....
Guys, I will address these all together as there is somewhat of a common theme.
In order for an Alpha 50mm bin to be a mainstream 'birding' bin, it needs to light - I'd suggest somewhere around the 900gram (~32oz) mark would be possible even with the old magnesium technology, and this would still retain all the SF goodies - great balance, sharp edges, negligible CA, wide Fov, and great (18-20mm) ER; +++
I would also think that a weight down around 850grams (30oz) or less is possible if Zeiss stepped into the 21st Century and went with a CFRP chassis - I don't care for blasting my bins with a shotgun, driving Hummers or Tanks over my bins - strong enough to maintain dimensional stability, and survive an accidental drop or pedestrian! stack will do .....
The opportunity is there to make the absolute best binocular in the world. After all, if the Swaro 10x50 SV was lighter, and with a few other minor nicety tweaks, it could realistically be a mainstream bin.
The notions that the 42mm SF has taken up some of the function carries some merit - up to a point ...... The one thing a 50mm can do that the 42mm can't, is deliver that 5mm EP at 10x. The others (54mm HT's etc) are too heavy and compromised to consider.
A 50mm SF would need to move the game on through several evolutionary improvements:-
1. Must hit that weight target ~850-900grams or less. CFRP, Titanium shafts, the works.
2. Must utilize HT glass prisms, and in other appropriate lenses to offer a perfectly neutral colour rendition and flat transmission curve (and as least Ed for one understands) to increase the brightness.
3. Must offer 70° AFov's along with that 18-20mm ER.
4. Must 'smooth' the distortion profile by offering a less radical slope and inflection point to the mustachio curve. This will address some of those who are seeing RB in the 42mm SF but not the SV. It seems that some degree of 3-D simulation (without losing the sharp edges) is also needed to compete with the NoctiVids.
5. Must improve CA handling so that results are no worse than the 42mm - more FL glass (helps with the lightness as well) - and there are other ways too!
6. Must move the glare control bar higher to be a clear leader.
7. Must sort the attachment and longevity quality of the armouring out while retaining lightness.
8. Must come to market fully sorted - no design, material, parts, supply, quality, delays as before AND DEFINITELY NO shipping of this early pilot, pre-production, and initial runs of product out the door to use customers as Beta testers. I would suggest Zeiss needs to soundly trounce the resolution standards so that even the most alien savant eagle eyed among us detects no spherical aberration, or softness.
9. Niceties would be a slightly quicker focus (in real terms) - I think 2m CF would be sufficient.
I would buy one of these in a heartbeat - especially the limited edition tan coloured perforated kangaroo leather model in 9x50 format :t:
Chosun :gh: