Apparently Tom Welling spilled to some people that season 10 is going to be the last season of Smallville, and I guess he's been given a hard time about it, but it's not like it's any secret. Smallville has already been going longer than anyone expected it to, and it can't go any longer because it's time for Clark to be Superman! I suppose Clark could go a few more years without being called Superman, but he was supposed to be able to fly when he was 18, and he's already 23 and still not flying. When they made the "No Flights, No Tights" rule when the show started in 2001, I don't think they expected it to still be running 10 years later. They probably didn't anticipate including other members of the Justice League, either, but that was a great decision. Superman without other superheroes is kind of boring, but he's a great leader for the others because he is the conservative one who brings balance to the team.
I am a loyal fan of Smallville, and I've been watching it ever since I saw "Bo Duke" was playing Jonathan Kent. I think it would be great if the show continued with Clark as Superman working with the rest of the JLA, but it can't be Smallville any longer than another season, because Metropolis is his city. Smallville is just where he grew up, and he's all grown up now!