Yes,you will only need to update HL2 through steam....Valve has said that everything you need for online play etc will be packaged with the retail versions...........
I don't see why it would come with the cache files for Half-Life 1 and it's mods/expansion... they'll already have enough space taken up by Half-Life 2 itself, without adding 700+ megs of five year old games...
It'll definatly come with the Steam front-end though, as that is an integral part of Half-Life2.
so if it doesnt come with steam, what will i have to download? steam then? anything HUGE for us dial ups?
cuz it would suck if i had to download 74mb just to play hl2....then it would be delayed till sep 30th 3003 =[
Steam itself is a 500kb application.. If Half-Life2 doesn't include it (Which I can almost garrentee it will, after all it's only 500KB) it will be a trivial download, even for someone on a 56Kb connection. Going at 6KB a second, you could get the file less than two minutes..