It always was fundamentally unhackable. It was built on top of Broadcom, which has completely closed documentation. Frankly, Arduino / Atmel is the only open platform from bottom to top. Oh, and PCs (Intel / AMD).

I don't think Windows is going to close any real bits of the Raspberry Pi 2, at least any more than it already is.

I'm actually more excited about "open" hardware like AMD AM1 or Intel NUCs for this reason.