Was Snape's betrayal set up from Bk4?

[lisamconley]

No: HPFGUIDX 132994

Potter experts help me out- This passage has been bugging me since I
finished HPB yesterday:

GoF p. 651:
Voldemort- "And here we have six missing Death Eaters...three dead in
my service.  
One, too cowardly to return...he will pay.  
One, who I believe has left me forever...he will be killed, of
course...
and one, who remains my most faithful servant, and who has already
reentered my service."

Does he mean Snape is and *always was* his most faithful servant???
Before HBP I thought Snape was the "one who left forever" and
Karkaroff was the "one too cowardly to return." I still wasnt sure
about his "most faithful servant", but now it seems that was Snape.
Maybe I'm missing somehing completely obvious, But now it seems:

too cowardly to return- Karkaroff?
gone forever- ????
most faithful servant- Snape?


Lisa