Other contributors have said "WHat year will Extra Terrestrials visit Earth?" is the same question as "Who are extra terrestrials?" If you believe that these are not asking the same thing and should be answered differently, click here
The "chances" of finding ET's has already been acomplished, as there are at least three beings in varied states of preservation, resulting from the Roswel crash of 1947.
Even though "sited" means "located", we have a hunch that you're asking where they were seen, or "sighted". The answer is: There has never been any credible evidence, that stood up to competent...