Will Parents visa get cancelled if the extension is rejected?

My friend’s parents have filed for their extension of stay beyond 6 months. They are planning to go after the 8th month of stay. In case, the extension request is rejected for any reason, will their visa be rejected/cancelled out and need to reapply for a new one? Do you suggest to withdraw the extension application if the approval has not come before their exit?

I many cases, if the B1/B2 extension is denied, they also cancel the visa stamp in passport. It depends on how the officer perceives the situation.