Will you be increasing the max players beyond 8?
We are exploring this possibility, though currently it is defaulted to 8 max players.
If you have multiple casters selected when you cast a spell, will they all cast it or only one? (ex. will 8 ghosts all use lockdown on a unit or only one?)
Currently, unit abilities are set as smart casting, meaning when you have a group of casters selected, each time you wish to cast a spell, you will either have to click the icon or press the hot key and follow it with a click on the designated place on the map for it to cast. This will obviously prevent locking down a single unit with more than one ghost, though we are also still exploring possibilities to have different methods of casting for casters in which players would want to have multiple casts executed in a single command.
Will building placement still be grid based?
Building placement will be grid based.
What races will be playable at BlizzCon?
This will be revealed at BlizzCon! See ya there!
Why do marines have shields now?
The shields seen on marines in screenshots and videos are an upgrade that can be purchased through research, increasing the marines' overall hit points.