I have a pair of Mavic Ksyriums, about 3 years old, not sure what the model is, they are fitted with an 8 speed casette.
I want to upgrade to 9 or 10 speed, anyone know if they will accept these casettes.
Yes, the odds are exceedingly high that you can fit either a 9-speed or 10-speed cassette on your freehub body (which is probably a Shimano compatible freehub body).
Same is true even if it a Campagnolo cassette ... I could fit an 8-speed, 9-speed & 10-speed cassette on my MAVIC Ksyrium rear wheel.