That's a silly question, Starcraft is still a professionally played game and will probably remain so for as long as the RTS genre exists. It's easily the best RTS ever made, thus why it remains on the top spot.
I've had SC since it was released and I still play it on and off every now and again. I don't enjoy playing it too much anymore since RTS was never my thing-- that coupled with the fact my brother is way too good at the game and beats me into the ground every time. I've always played SC with the same circle of friends since release and I would say my brother occupies over 95% of the wins. (That equates to about 6,000 victories since we have probably done a lot of matches over the 10 or so years that SC has been out. I also recall his first Battle.net account having 3,000 or so victories) Shame he doesn't live in Korea or something, he could make a living off of SC matches.
Anyways, as long as SCII isn't just superior to SC one in every way, odds are it will be around for a long time. Hell, Street fighter II is still played in tournaments and it's old as hell.
"There once was a boy who dreamed of being a hero. Who believed sincerely in the battle to banish darkness from a world of light... but light and darkness are equal... and where one exists so too must the other... and when the boy finally realized this he had taken the first step toward being a true hero."