The PC Beta will be pushed back to early next year. However, DICE hasn't left us empty handed. They have released the PC features of Bad Company 2.
 
DICE Producer Gordon Van Dyke in his words:
 

Hey all,

We wanted to update you, and slow the flood of tweets, on questions surrounding the BFBC2 PC Beta being cancelled. I'll get right to it and say "the BFBC2 PC Beta is not cancelled". Now this all started due to changes made to an earlier blog that removed the PC Beta from the details and the reason for this was the plan changed. With the huge success of the PS3 Beta we decided to drastically increase the PC Beta's capacity to insure as many people as possible could participate. Unfortunately this meant we had to delay the Beta to very early next year giving us more planning time to make it happen and implement more optimizations.

Here is a recap of the current PC features, and we can now confirm DX11 support with more details to come later!

PC Enhanced Features

• Up to 32 Players on PC (24 on consoles) - Play with up to 32 players online in the biggest multiplayer Maps in Battlefield. Each with a different tactical and gameplay focus set across a variety of environments.
  
• Full DirectX 9, 10 & 11 Support - Immerse yourself in the Battlefield world as Frostbite engine brings tanks, planes, and explosions to vivid life on your PC. The game will fully support Windows XP, Vista, and 7 with new tech that further improves things like lighting and shadows.
  
• Enhanced Gameplay - The PC version also includes wide peripheral support like Joysticks for flying, NVDIA 3D Vision, Logitech LCD Keyboards and VoIP Support plus a variety of specific features tailored for PC play.
  
• Friend Support - Find your friends online with the new buddy list to see if and who is online so you can quickly join their game.
  
• Dedicated Ranked Server - Everyone gets non-stop action with no connection penalties based on some other player's internet. Ranked Server Provider program will give players opportunity to rent their own server(s) located in professional grade datacenters, ability to modify settings like map rotation, create reserved slots for friends or clan members, kick & Ban players, and custom name your ranked server.
  
• Clan Support & Private Servers - Independent Clan Tag, and ability to rent servers for hosting and controlling private password protected competitive servers with expanded control over the settings from public ranked servers.
  
• PC Squad Play System - Updated from previous Battlefield PC titles now gives control of your squad before heading into combat.

I'm curious what the Squad Play System is. The description doesn't tell enough. Do they mean manually choosing squads instead of being put into a random one?
 
Honestly I expected them to cancel the PC beta altogether. But since it's been pushed to early 2010, I'm betting the actual demo won't be out along side the console demos in early January. Which also makes me think the actual game releases will differ instead of being simultaneous.
 
edit: also, Planes in BC2? How did I miss this?

Dedicated Servers and 32 player support? BLASPHEMY!

edit: also, Planes in BC2? How did I miss this? "

Kind of funny how I would not have given this game any thought if it weren't for Modern Warfare 2.

" @MrKlorox said:

edit: also, Planes in BC2? How did I miss this? "

I wouldn't count that as a confirmation of flyable aircraft just yet. He may have been referencing the A10 Warthogs that fly past when you progress to another section of the map. "