i think the most likely extraterrestrial contact will be via 'intelligent" probes, no not the anal kind. these probes would only disseminate information. you have to factor in the distances involved. what is the point of gathering information if it takes you a 1000 years to get it? the idea is not to have a two way conversation but to let other possible civilisations know you are around. the sender of the probe may even have ceased to exist by the time we get it.