I thought the show ended well actually, its not at ALL a "sad" ending imo - his father/uncle alive, possibly 2 new allys among the machine people (John Henry and the Garbage singer), it goes back to the roots of T2 and "the future is what you make of it", instead of the "can't change anything" T3 message.

Sadly the new movie has absolutely nothing to do with the TV show and the two have no story lines in common other than involving terminators and John Conner.

Re: why it was cancelled, obviously viewership numbers weren't great but its also a numbers issue. Dollhouse for example is produced by Fox and they own the IP, whereas they have to license the Terminator IP from Warner Bros - season1/2 was licensed very cheap because WB wanted the universe in peoples minds before the movie. Also shows like Dollhouse and Chuck agreed to significant budget reductions going forward, it would have been hard for a special fx driven show like Terminator.

Its a bummer, next year may be a pretty dry sci-fi year. Lost is winding down, the only new shows afaik spinning up are Stargate Universe and Caprica, I think the quality on both will be pretty uneven (some good episodes lotsa crap).