Nokia has sent out invites to a few Russian Windows Phone sites, including WP7Forum.ru for an August 28th event. The invite, always a good source for clues, simply shows a piano keyboard along with the “world premier” and date written across.
Speculation on the conservative side would suggest the launch of Nokia Music, but that is already up and running in that region. Perhaps a keyboarded device? Maybe but so far there has been zero indication that Nokia would make such a phone, in fact, they have been adamant in the past that they won’t. And as WP7Forum point out, it would be odd to have a “world premier” for an accessory, though we suppose anything is possible.
One cannot also discount the possibility of another Asha series device, which would have little implication for Windows Phone users. Finally, the device in question could be a Lumia tailored for the Russian market, akin to the Lumia 928 for Verizon.
But at this point, there is little to go on—probably just the way Nokia likes it. We’ll keep digging though for clues.