The founders of Ripple Labs created 100 billion XRP at Ripple's inception. No more can be created according to the rules of the Ripple protocol. Of the 100 billion created, 20 billion XRP were retained by the creators, seeders, venture capital companies and other founders. The remaining 80 billion were given to Ripple Labs. Ripple Labs intends to distribute and sell 55 of that 80 billion XRP to users and strategic partners. Ripple Labs also had a giveaway of under 200 million XRP (0.002% of all XRP) via World Community Grid that was later discontinued. Ripple Labs will retain the remaining 25 billion.
'nough said
How many did Satoshi hold again

? Or on a different note, how much of all coins in existence at the moment are held by the top 1000 adresses?
But to fill you in on how this works: 55 will indeed be distributed if I'm not mistaken, the remaining 25 billion will remain locked up until there is a use for it. Also: the founders are all bound on holding onto their XRP via lockup agreements. But you could find that on the internet, although I have this feeling that you already knew this.