Julie Delpy recently said she collectively discussed an idea for a fourth "Before" film with Richard Linklater and Ethan Hawke, but they decided to not move forward.
“What happened was that we - all three of us - agreed that we couldn’t come up with something good for a fourth one. It’s that simple. We didn’t fight. We’re not on bad terms. Everyone’s happy... It’s so much drama for nothing. We just didn’t come up with a good idea.”
Delpy has now confirmed that Linklater proposed the idea for a fourth entry, but she declined.
As sad as this news may be, I guess we've got the perfect trilogy and we can revisit it whenever we want.