from gaf :
Some things I learned talking to a Capcom Vancouver rep:
1. They will not be talking exact resolution nor framerate at E3, but frame rate is already improved from DR3.
2. Game is already running more zombies on screen than DR3.
3. There will be more variety of zombies than DR3.
4. DR4 uses improved version of DR3 engine. Development started 8 months after finishing DR3.
5. Capcom Vancouver is developing, MS is pubilishing. 1 year exclusive with MS. Slightly different deal than DR3.
http://www.neogaf.com/forum/showthread.php?p=207130888#post207130888