According to F4Wonline.com, Shinsuke Nakamura confirmed with a Japanese newspaper that he is in fact leaving NJPW at the end of the month when his contract runs out.
No confirmation yet if he mentions signing with the WWE due to his current contract, but you would have to think that with everything that has happened, it is looking more and more likely.
If you are unfamiliar with Shinsuke Nakamura, do yourself a favor and Youtube him... Widely considered one of the best wrestlers in the world.