Snape and the DE's

[Lisa]

No: HPFGUIDX 23151

At the end of GoF, we are led to believe that Snape will be going back 
to the DE's to spy for Dumbledore.  But how can he believable as a DE? 
 In SS, while Voldemort was living in Quirrell's head, Snape was 
outwardly battling Quirrel to prevent him from injuring Harry and 
obtaining the stone.  Voldemort had to be aware of that, so how could 
Snape now go back to Voldemort without seriously risking his life?  

In fact, on page 651 of GoF, Voldemort says of the DE's missing from 
his company, "One, too cowardly to return...he will pay.  (Must refer 
to Karakoff)  One, who I believe has left me forever...he will be 
killed of course.  (Must refer to Snape)...and one, who remains my 
most faithful servant, and has already reentered my service. (Must 
refer to Barty Crouch in the guise of Moody)"

Clearly Snape is putting himself at great risk, and he must be aware 
of this.  Perhaps Snape is the one who will die in Book 5?