I see all over the internet that Intel Atom based devices are going to be launched which will be x64 based processor. Do we have any devices (WP) which have x64 or x86 processor? Or do we expect them to be available in near future?
Do we have any devices (WP) which have x64 or x86 processor?
No.
do we expect them to be available in near future?
There are some rumors, but I doubt they will. ARM is good enough, and since WP8 allowed native code development, there're now too many platform-specific apps in the store.
What you can expect — Windows might increase its share on the tablets. For example, HP Stream 7 costs $80, and is based on x86 CPU.
If you are considering to develop a mobile app and deciding whether you’ll need to support x86/x64 — I think the answer is “probably”.