One of the reasons Starcraft is still such a big hit at LAN parties is that, like most "older" PC titles, it supports multiplayer over a local network. Starcraft II will do no such thing.
Blizzard's Rob Pardo has said "we don't have any plans to support LAN... we will not support it". Which for anyone that still lugs their PC around for LAN parties means no, Starcraft II won't be on your LAN party menu. If you want to play against other humans, it'll have to be done via Blizzard's online gaming portal Battle.net.
Which will no doubt be crushing to LAN party fiends... if, that is, they still exist.
StarCraft II Developers Talk [IncGamers]