The hire won't necessarily change the state of affairs for Apple, which has had to make do without Lattner for months, but it's a definite coup for Google. Lattner earned praise for Swift because it was fast, thoroughly modern, and (most importanty) accessible -- everyone from first-timers to seasoned programmers stands to benefit from it. Google could put that know-how to work making TensorFlow easier to use, or lowering the hardware demands so that AI runs more smoothly on phones and computers. There's no guarantee that he'll repeat his previous feats at Google, but the potential is certainly there.