Here's a video interview I found with Capcom explaining that DMC5, which will take place were DMC4 left off, is already in development and will be released sometime next year.
Here's the full interview. Its really interesting stuff, check it out!
http://www.youtube.com/watch?v=x4WuFU6XV_o
"We never had any intention of dropping the current Devil May Cry series." Capcom representative explained. "However, we wanted to branch out the DMC universe and attract new fans, leading us to develop the DmC reboot." he then went on to say, "Don't worry, we haven't forgotten about Nero and the others."
Here's the full interview. Its really interesting stuff, check it out!
http://www.youtube.com/watch?v=x4WuFU6XV_o