I couldn't find any date on Kensington's site.
The product page on Amazon just lists it as 'currently unavailable' with no release date.
Here is a cached amazon page listing its release date as August 4...obviously that date has already come and gone with no release.
I am interested in this one too -- it looks very very close to the Elecom DEFT Pro size and layout. I am a big fan of the Kensington scroll wheel, and hopefully they have better bearings/smoothness/QC than the Elecoms.