My opponent has a {Jace, Archutect of thought} out and +1s him so my creatures get -1/0 if it attacks.
Now say I Precombat main phase a {Dreadbore} to kill the Jace. Do my creatures still get the -1/0 even though Jace is no longer there?
Yes. It creates a delayed trigger that is separate from Jace and doesn't care if he's still around.
RESOLVED
Thanks! :D also liking that new profile pic of Chandra it looks sick :P