Php (Personal Home Pages) is already something it was never intended to be. It's the "hey thats a nice feature, let me add a crappy implementation of it" language. If you mean "turn PHP into something never inteded to be" as turning it into something not absolutely horrible to work with then OK. Anything they do is going to be better than PHP. You would have to try really hard to make it worse.
People always moan about how horrible PHP is, and I always assume that the people moaning are trying to learn the language without having a basis in C because they have come straight from Ruby or some other perfectly designed load of academic twaddle nobody uses.
The reality is that PHP is like C, an amazingly flexible and well used tool. Yes, it has tons of quirks due to its slow evolution where they maintain backwards compatibility, but that is it's strength in the real world since nobody wants to rewrite their entire system just to use a new version of a language.
There are tons of things better than PHP, but PHP is more well used than all of them because the purist developers who like to create perfect systems generally do not create much. The people who do are the armchair warriors who throw together something like Facebook then realise they have created a horrible puddle of code with a ton of technical debt that just happens to be a popular product that actually makes money. The purists have a habit of getting bogged down in producing wonderful code that takes ages, never makes any money and so get consigned to the scrap heap when the company folds.
What they have done is layer a statically typed language on top of PHP so that they can still run their existing PHP code as they slowly convert it to a typed language. Maybe their end game is to move away from PHP, but maybe they will stay with Hack to they can carry on recruiting PHP developers who then have an easy transition. This is another reason why PHP is so popular with companies: commercially experienced PHP developers are much easier to find than commercially experienced Ruby developers, or even Python.