I read somewhere an article the other day on a Sphynx that died at 35 but I think he was the exception not the rule. I don't see why a Sphynx would be different to a normal cat and have same life span on a arrange but like us humans they all different too so like us can't really predict
I don't think one breed has a longer lifespan than another, just some breeds seem more predisposed to illenesses like HCM, but if you can avoid that then I've heard of cats living well into their teens.
According to the books - the oldest sphynx cat (possibly even the oldest cat in general - part Sphynx, part Rex...I wonder what he fed him?) lived to the ripe old age of 34 I believe - here is Grandpa Rex Allen's 32nd birthday party.
One of the oldest cats on record. Granpa Rexs Allen, a sphynx, was adopted from the Humane Society of Travis County (Texas) by Jake Perry on January 16, 1970.