I-94 date when entering on Visa expiring in a month

[letsplaysudoku]

Hi,

- My current Visa expires on Sep 30, 2015

- I would be travelling to India and be back in USA on Aug 22, 2015

- I'm not planning to get my Visa Stamping done while I'm in India

- I would be entering the US on my old Visa, but hopefully by then will have my new I-797 for my Visa extension with me as well.

- How would my I-94 dates be handled ? Will it be stamped to my new I-797 date or only till Sep 30, 2015. If it's till Sep 30, 2015, will it be an issue to stay post Sep 30, 2015 though I have a new I-797 ?

 

Thanks for all your help.