Is Popularo going to be a Digg killer?

NO.

The question should be restated: Can Popularo become a better community than Digg?

Digg is a community, not a technology solution. These two are different things completely. Popularo is trying to build a community, not a competitive technology. While I realize that communities can be competitive against one another (for example war), I don't see the two as competing for anything other than participation, which is something that is not exclusive to either.