Zeiss announced the first ZFs, 50/1.4 ZF & 85/1.4 ZF, Jan 1 2006, and then announced 4 more in Oct 2006 for Photokina, the 35/2 ZF, 25/f2.8 ZF, 50/2 makro ZF & 100/2 makro ZF according to news stories over at DPR. If Zeiss follows the same pattern and announces an Otus 25/2.x at Photokina, I'll soon be buying my first $4k+ lens. Sure, no guarantee that the same pattern will emerge but a fellow can dream. Zeiss may be more cautious rolling $4k lenses than they were releasing $500 to $1k lenses back in the day.
I think the news is out on the Sigma 50 ART, no cigar for competing with Zeiss wide open.