There are currently ~7M (as of August 2011) in existence and  it is expected that all 21 million Bitcoins will have been generated by 2033. Whereas there are currently ~580K Ixcoins (as of 10th August 2011) in existence and it is expected that all 21 million Ixcoins will have been generated by 2015. Ixcoin maturity will be reached ~18 years before Bitcoin's.