They aren't promotional (well, they are), but they won't all be out before the game launches in 3 weeks. Expect another just before launch then periodically up until Christmas or so.
The game isn't finished yet. Most every game through a Beta stage where it is tested for bugs, glitches and general faults in the game by independant testers, think of it as a new angle - a parent will see their child as perfect whilst the rest of the world can see how ugly it is.
A lot of multiplayer games are given a public beta so that the company can test the game in a situation that may be difficult to recreate artificially i.e. server strain and lag problems.
The game then be fixed up and ready to ship in a good, already tested condition.
The game seems pretty much finished, though one thing I have noticed is that almost all of the objects on the levels are fixed and non-destructable...I hope this changes when the game is officially released.
As for the 'meet the' videos...I have shown them to all my friends and everyone has found them very funny. They are a great way to advertise the game, most people obviously won't know what Team fortress is, so it is a great way to generate interest by giving people a laugh and showing them what that class is all about.