does it have a chance of blowing out and draining all the oil? or is that very very late?
even if it blows wouldnt the metal between the transmission and engine act as another seal so that all the oil doesnt leak out?
I would say it's very rare for one of these to leak as badly as you're worried about happening. Chances are it will continue to leak slowly for the life of the vehicle. My 05 4.8 is also, it's difficult to be 100% sure it's the rear main until you remove the transmission. Mine goes through more like 1qt per 2k miles and it's still no big deal.