In an interview on Community Fortress Valve's Robin Walker said "We've got multiple updates in the works still, at least one of which will land before the Engineer pack. As always, we haven't planned too much out beyond that point, because we want to see what feedback we get from the community."
The Engineer is the only class that has not yet received a free update containing new weapons and a set of achievements. It's good to hear that even after this has been released - and who knows when that will be - there will still be plenty of new updates for gamers who enjoy pwning noobs in Team Fortress 2.
You can discuss Team Fortress 2 here.