I wouldn't be surprised if they find nothing.
I have a suspicion that civilisations may follow two general paths;
one is that very few civilisations actually sustain a technological high long enough for their radio emissions to be obvious. In other words, as we're finding, they reach the limits of their planet's resources and their society effectively collapses.
Or, the period in which a civilisation uses radio and other 'visible' radiation is relatively short. Thereafter radio communications are replaced with 'invisible' quantum effects such as particle entanglement - which we can't listen in to. If that's the case, the galaxy might actually be abuzz with messages, but we wouldn't know anything about it.
I have a suspicion that civilisations may follow two general paths;
one is that very few civilisations actually sustain a technological high long enough for their radio emissions to be obvious. In other words, as we're finding, they reach the limits of their planet's resources and their society effectively collapses.
Or, the period in which a civilisation uses radio and other 'visible' radiation is relatively short. Thereafter radio communications are replaced with 'invisible' quantum effects such as particle entanglement - which we can't listen in to. If that's the case, the galaxy might actually be abuzz with messages, but we wouldn't know anything about it.