The kilogram has been redefined in a way that does not refer to the International Prototype Kilogram. That kind of makes the International Prototype Kilogram useless.
So what will happen to it? Can I have it?
Can I have it ?
The 1 Kg block of metal is 90% Platinum and 10% Iridium.
At today's prices on the commodity market that will cost you about USD $ 29,237. You can try emailing the owners, but I suspect they'll pop that sucker in a museum (or hang onto it as an investment). The actual value at auction would probably be considerably higher given it's history (and that's probably ten or a hundred fold, not just a few dollars more :-) ).
In fact it's essentially in a museum now, as it is kept in strictly controlled conditions and no one touches it (to avoid altering it, quite apart from it's monetary value).
That kind of makes the International Prototype Kilogram useless
Not necessarily. It's still a reference mass and may have legal value in keeping in the event that some (odd) legal dispute pops up where someone makes an issue about the historical value of the kilo.
There is a need to keep things like this simply so you have a complete record of the standard.