We already are surpassing radio to become something that is undetectable in space. spread spectrum and low power communications is already common place in the Ham Radio community. with 2.5 Watts I can talk to 30 people around the globe using PSK31 or Wspr. My signal will not be detectable past the moon even on the best radio equipment made. High power broadcasting is a thing of the past and will rapidly disappear. Some of these new technologies will make communicating with our own space probes easier, but hellishly harder to detect as power levels can be reduced.
A very advanced species will not be broadcasting at 200,000,000,000 watts with AM modulation or CW... what can be detected at light year or more distances. they will be using things that are far more efficient and will not be detectable. Honestly the whole SETI project is not looking for ET's TV stations or regular communications, it's looking for an intentional ultra high power beacon that was sent for the only purpose of saying "WE ARE HERE" which even reduces the chances of it being successful even more.
For SETI to detect a signal from Alpha Centauri. IT would have to be 10,000X stronger than any transmission ever sent from earth and on a constant time year after year after year so that it can be detected.