In a msg on , Audrey Falconer of 3:632/522 writes:

 AF> I can. I could never stand Blake. Or Tarrant, for that matter.

 AF> The real question is: who was left alive afterwards? Vila dropped 
 AF> at the sound of the first shot; we didn't see him being shot; 
 AF> Dayna and Soolin were hit and fell; Tarrant was already injured 
 AF> before he was hit and fell. Avon was definitely still alive and 
 AF> armed. The only one we are *sure* is dead is Blake.

 AF> At the time it was made there were thoughts for a fifth season, I 
 AF> believe.

the story I heard (admittedly "nth" hand) was that the BBC
management said "Enough... End it" at the end of the third
series.  Terry Nation stormed out and went to work for Winkler/Rich on the
MacGyver pilot, and so it more or less just ran out of steam.

Then again the only verifiable bit of the story is that Nation did take up 
US residency around the time that the fourth series was being made.

Cheers,

--- msgedsq 2.1