Now the 10-18 f/4.5-5.6 IS STM & EF 16-35 f/4L IS are available for preorder at B&H for US$299 and US$1,199 respectively. You can press the keyboard now.
For those with APS-C sensor, the 10-18 f/4.5-5.6 IS STM in this price is quite reasonable for an UWA lens. I don't think I would buy the FF EF 16-35 f/4L IS, since I have the f2.8L II version but time will tell.
The MTF charts are very promissing in terms of IMO, it indicates huge improvement in sharpness from mid-frame to borders.