Valve has hired Icefrog, the gamer who currently maintains Allstars, easily the most popular original Dota mod. We can thus expect the core game mechanics to remain somewhat similar. The full roster of heroes from Allstars will be brought over, along with items, upgrade paths, and skills. The migration to the Source engine will however bring a few changes, including some graphical upgrades and added voice chat. The Dota 2 team is also reworking the visual style to accent important information, and more voice character lines will be introduced. Valve wants to keep the focus on multiplayer, but bots will fill in for disconnected players and for skirmishes.
Valve plans to add match-making, guides created and voted on by the community, and a new coaching system to help ease in new players. Veteran players will be able to log in and offer guidance to new players, and receive feedback for their good work.
I'm a huge fan of DotA so I'm particularly excited about this release. I just hope Valve won't butcher this great series. What are your thoughts and hopes for Dota 2?