What I'd love to see is the pipe launcher back from TFC. It's basically the current sticky and pipe launcher at the same time. It shares the same ammo but the "stickies" don't stick, they just bounce around like the normal pipes. This would be the primary weapon. It would remove the stickies!

Though, you are screwed when you can't aim 'cause you just can't switch to the winbombs when you're out of ammo...
Since you only have this weapon and the melee weapon, Valve could add a brand new weapon for the demoman. You either choose the Pipes and the stickies or the classic 'nade launcher and the new weapon. Unless Valve would just make the classic pipe launcher two weapons with the same model etc... That would suck.
Gimme my TFC Demo!
-Calle