As I was employed by Mongoose at the time and preparing to convert the line over to MRQ2, I know exactly why the Conan licence was let go - sheer greed from Paradox Entertainment - who, inspired by the (then) in production movie, imagined that they could demand excessively more money. Despite a profitable d20 line, the new price far outstripped the previous licence cost and so Mongoose had to let it go.
As for the Elric licence, it was never as profitable as Conan. With Mongoose's ever diminishing revenues, they were forced to let it go... or possibly had it yanked from them, since they lost the Lone Wolf licence at about the same time. I'm unsure of the exact reason because I'd left well before this, but I have some insights.
In the future I don't expect the Elric licence to be snapped up, since most young gamers haven't even heard of the albino anti-hero, let alone read the books. So the market is small.
Conan will stay out of everyone's reach until Paradox either gets realistic about how much money an RPG line can earn these days; or somebody has the courage to publish a game based on the copyright-free stories without giving a damn about their Trademarks (and hopefully a sympathetic judge who still values the concept of Public Domain).