If they're smart, they will allow him pretty much free reign, and then put some resources behind his projects to help them mature. (think Sergey Brin or Andy Rubin at Google)
On top of that, Facebook has shown itself to be untrustworthy many times from a dev and user perspective (beacon, FB credits etc), so if Carmack wants to avoid that and produce something without intrusive advertising for example, they may well clash.
None of this means it was a bad idea to sell for oculus, just that selling is ceding control completely to the vision of the larger company in the long term.
I mean, hacker news likes to freak out about fiduciary duty and "omg, corporations are obligated to make maximum profit." But realistically, almost no big corps run that way (almost all engage in some charity, many have foundations, etc.), and there is near-zero legal possibility of minority investors forcing them to. This is because investors have almost no say unless it is obvious you are trying to screw them -- normally a subset of them -- or unless there is no plausible way a course of action could make money.
Engaging in charity and supporting foundations is not related to the "generosity" of the a corporation (who runs it); charity and foundations can be PR and tax-saving strategies.
Drug cartels engage in charitable donations; that doesn't make them generous.
HSBC (just picked a random one) supports charities. It also launders money for the drug cartels and is generally involved in illegal money transactions.
I can pick virtually any big corporation involved in corruption/crime scandals and I'm pretty sure they routinely make charitable acts and/or have their foundations and as well.
I certainly don't say that any corporation is corrupt, but the link with foundation/charities and morality of a corporation just doesn't exist.
- A real state company that helps an organization that seeks to prevent the construction of new buildings (because it destroys the forest/parks) but in reality they just want to keep the price of their own stock as high as possible.
- A clothes company that support anti-fur organisations, only because the rival brand is the target of such protesters.
- An alternate reality where Shell supports anti-Exxon campaigns done by Greenpeace.