The treatment in 2015 of disgraced Cardinal Keith O'Brien (formerly head of the Catholic Church in Scotland) suggests that it's very unlikely that a Cardinal will ever lose his title.
O'Brien resigned (or was required to resign) from "the rights and duties of a Cardinal", but he was allowed to keep his title. Even now, he remains styled as 'His Eminence'.
Resigning the rights and duties of the role: this would include losing a vote in any Conclave to elect a future Pope.
BTW, I don't personally agree with this generous treatment of disgraced prelates. But this is the way the Church operates.