L1 blanket extension,rejection before the expiry of current visa

[bipnis]

Hi

I am on L1B blanket. My visa expires on 31st Dec 2012.and i 94 expires in April 2015.
My company policy requires valid L1 visa to stay in US.They dont consider validity of i 94.So they have started the process of extension application.
My question is, If my L1 extension application gets rejected before 31st Dec 2012,(say 30th November)do we have to leave the country within 10 days of rejection notice..Or Can we stay until 31st Dec 2012. I read somewhere, when our extension is rejected ,that is our status with USCIS,not our current valid visa.Is it true ???

Thanks