Lukas Smith has posted some of his own thoughts on the Liip blog about the future of PHP, HHVM and Hack (related to this previous post from Anthony Ferrara) in the context of the company and the work they're doing.
I want to specifically comment on the part about HHVM and Hack. I have of course published my own opinion on the topic fairly recently on my private blog. Fellow Liiper Chregu has also done a very popular post on this very blog showing some very significant performance improvements that can be achieved with HHVM. [...] While Anthony does not recommend running HHVM in production, we are obviously getting ready to do just that. I totally agree however with the risks he points out.
He talks more about using HHVM in a production environment and some of the possible problems with it in the future (like maybe a change in it being incompatible with PHP someday). He also touches on the Hack language and how it is possible that Facebook's team will go wholly with Hack instead of PHP.
One of the big questions is why does Facebook even care about PHP mode if they are already moving their own code to Hack? To me one big reason for this could be that they actually want to use code produced in the community. [...] So maybe in the end the best way to ensure that PHP mode in HHVM remains a goal for Facebook is to keep churning out high quality PHP code?