They changed it to give the survivors more of a challenge. In l4d1, everyone would just camp the stairs, making the finale very easy. Frankly, I liked the old version better, and it would've worked with l4d2 because of the spitter. Oh well.
First off, don't trust the overwiki, they put in so much crap its hilarious. Why do you think that we'll visit just the dock that didn't vanish? Why not the whole ship? I see no evidence against the latter possibility.
And thanks for the article, I kinda hoped that portal happened before hl1...
Episode 2 will work by itself, in that the game will operate correctly, but its a crime to play episode 2 without playing the other games in the series.
Willing to bet money that you pirated the game. Anyway, if it happens again just noclip through the bits that don't work (type sv_cheats 1 and then noclip into console), or just load the next map (type map *** in console, where *** is the name of the map).
Its just one of those things game devs use to keep the game together. There are also hundreds of times when Gordon could simply climb over a 5 foot tall wall, but no, he had to go 50 zombies or combine or HECU.
I really, really doubt that they'll call it HL3. Besides that, it might very well be long enough to be considered a separate game. Ep2 was much longer then Ep1, so if that trend continues, (it looks like it did) ep3 will be longer then ep2, making it roughly the length of a full game.
Welcome to hl2.net zachary, and you're right, when you put npc's into the source that the source engine doesn't expect to be there, you get a whole lot of lag. Its cause the engine has to come up with a set of actions for each npc, which gobbles up a lot of recourses. You get this in gmod a lot...