I’m not surprised Valve’s visited Weta workshop, if I remember right, Valve hired one of the prominent individuals who worked on animating Golem’s face to assist them in improving their facial animations. I wouldn’t be surprised if Valve has spoken with Weta digital about licensing proprietary software and the like to help improve the source engine. Newell probably dropped by Weta workshop afterword and asked if they might make him a sentry.
I wouldn’t read into anything, though. Right now Weta workshop is probably got their hands tied with The Hobbit preproduction and won’t have time for very many other projects for a good long while.