Nobody really knows for sure, that's the truth - Vini is well settled at Madrid, making way too much money and playing for a team that competes for titles every year, so the chances of him leaving voluntarily are pretty slim. Rumors about him coming back to Brazil pop up here and there in the press, but they usually come from weak sources or are just based on speculation, like those articles that try to guess what the player's future holds. What matters is that he keeps renewing his contract and saying he's happy there, so for now it looks like he's staying put.