Agnt10, you are right that once you file visa extension, you can stay until you hear about approval or denial of your extension from USCIS eventhough your I-94 has expired and it is still considered legal stay. Yes, if it's denied, you might have a very short time to leave the country, But I am not sure if the person has multiple entry visa, that's going to be cancelled for next visit.

Has anyone been in this situation? feed back pls.

Thanks.