There is no planned Cannon Island on Poptropica. There is some speculation about a "military" island, but they are all rumors until officially announced. (Wherever you heard that from was a bad source.)
On a Island
the cannon is in booga bay too the right until you find the cannon
it is on the islend that looks like a scall
First you have to buy a ship from the Chinese guy on the Chinese island. Once you do that your new ship will have a cannon in it. Your raft does not come with a cannon You may need to take out a loan to buy a ship :)
Early poptropica
it costs 20,000 doubloons
Spy Island, the sixth island of Poptropica, was released on September 9, 2008.
Shark Tooth Island was the second island on Poptropica and premiered in September, 2007.
24 Carrot Island is the 4th island of Poptropica. It came out in June, 2008.
Time Tangled Island, the third island of Poptropica, was released in July 2008.
the cannon balls are underneath the cannon
When you finish poptropica just wait for the next island to come then you are not finished