"Jose" wrote in message
news

Assuming IMC, what does a controller do to ensure separation in the air
for the departing aircraft from an arriving IFR aircraft who has not
cancelled IFR or landed?


He applies an approved form of separation. There are a variety to choose
from, visual and radar are probably the most commonly used, but there are
nonradar techniques as well.

http://www.faa.gov/atpubs/ATC/Chp6/atc0603.html



Or is your comment limited to VMC?


Nope.