They don't, thankfully, but their idea of sufficiency is taking from others, so since sufficient resources exist in the galaxy to inhabit essentially all of it, they could eventually, conceivably succeed. Long-range communication is less of a problem than you'd think--various FTL comm networks span portions of the galaxy already, it's just a matter of the technology existing and the infrastructure being in place.

*She nods understandingly.*

The logistics of it are daunting. The Galactic Federation is the largest hegemony in the galaxy, and it still doesn't claim anywhere near the whole thing.