[PubQ] Is it true that agents are open to duo/trilogies these days?

I've heard from an agented friend that recently the "standalone with series potential" limitation is loosening up. Obviously, you probably won't have success pitching a 10-book series right off the bat, but I'm curious: has anybody else heard that you can pitch a duology or trilogy to an agent? Or is it still best to keep your manuscripts completely self-contained?