There has been no definite word on the location of the 2010 Bionicle story.
Rumors that it takes place underground on Bara Magna could be traced back to the topic linked below on Eurobricks. These are in no way confirmed, as the topic is a fan project to create a non-canon storyline for 2010. However, Greg Farshty stated that Teridax is coming to Bara Magna, hinting that is where the story will take place.
The setting for Bionicle 4 is on a planet called Bara Magna.
No.
Rumors said that 2010 may take place underground of Bara Magna where the Glatorians discover ancient ruins
the island is called Bara Magna
No there are only 4 Bionicle books,Bionicle ChroniclesBionicle AdventuresBionicle LegendsBionicle Super Chapter Books (The Unofficial Bara Magna Trilogy)
That has not been revealed yet, but we know it will have something to do with Mata Nui, because that will be when he crashes into Bara Magna.
The story line for the 2010 bionicle is this. After mata nui defeats tuma, he goes to the black spike mountains to look for this cube. He finds it, and a huge robot body that he thinks can stop makuta. He goes in it, and takes his mask off, thus letting his spirit into the body. After that happens, Makuta senses him, and goes to Bara Magna. There they have a giant battle, which is where the bionicle stars come in. They just get golden armor and stuff to defeat makuta's armies that gresh let go on accident. Mata Nui makes makuta use a gravity power to bring the moons of bara magna towards the planet. As one of the planets is coming by, mata nui pushes makuta into it, and it hits him in the back of the head. Makuta dies right there, and mata nui brings back all the plants and water to bara magna. Then all the toa, matoran, agori, and glatorian live together on the new planet.
The prefix "Ga-" represents water in the matoran language. In Bara Magna, Tajun is the land belonging to the water tribe.
Makuta and Mata Nui battle in giant robot forms, then mata nui makes makuta use this gravity power thing to bring the moons of bara magna to the planet. Mata nui pushed Makuta into on of them and it makes a giant hole in the back of his head, killing makuta. then all the plants and water return to bara magna, and toa, matoran, glatorian, and agori live happily ever after.
First of all, I'd like to point out that Mata Nui is never a "bionicle," but is a bio-mechanical being. "Bionicle" is a portmanteau of the words "Biological" "Chronicles;" Mata Nui is certainly not a story, but a being! ;DAnyway, Mata Nui has been seen in three forms - as a "great spirit" in the MU, as a mask (when sealed in the Ignika), and as a "toa" in Bara Magna. Pictures can be found here - http://biosector01.com/wiki/index.php/Mata_Nui_(Being)
They either live in the Matoran Universe, which has places like Mata Nui and Metru Nui, or in the Spherus Magna universe, which is outside the Matoran Universe and houses places like Bara Magna and Bota Magna. Heck, they could live in places other than that, the story just never got that far.
The upcoming 2009 BIONICLE movie will not be about the Mistika and the Phantoka, nor will they be in the movie at all. BIONICLE: The Legend Reborn will focus on the character Mata Nui, and will tell the second half of the 2009 story line. When Mata Nui, who has been trapped inside the Mask of Life and flung from his universe, lands on the planet of Bara Magna, he uses the power of the mask to create a new body for himself. While attempting to find a way off the planet and back to his body, he finds himself in battle at Arena Magna. After winning a battle in the arena, Mata Nui is asked by the Agori to fight their enemy Skrall and the Bone Hunters. A teaser trailer of this movie was handed out on a USB flash drive to those at the 2009 Toy Fair in New York City. A copy of this trailer can be viewed on YouTube: http:/www.youtube.com/watch?v=YZkPKrNEZBY