This is the closest to real news about GTA VI we've had in awhile thanks for Bloomber. Some highlights are below.
Bloomberg ArticlePiggybacking articleBloomberg states that there will be multiple protagonists and one will be a latin female. The also claim that it takes place in a fictional "Miami"/Vice City and it's surrounding areas.
The game has been in development since 2014 and they say it will likely still be two years away. Plans for having the game take place in multiple locations across North and South America have been scraped.
Overall, take all this with a grain of salt.