There’s no official word yet, but a public listing on Walmart’s website may have jumped the gun in revealing that Portal will be added to the upcoming LEGO Dimensions toys-to-life game. The Portal add-on was listed as a “Levels Pack”, which means that Chell (and maybe ATLAS and P-body?) will be playable in LEGO Dimensions.
Shortly after the news began spreading over the Internet, Walmart removed the listings. Screenshots and Google caches verified that the listings were indeed legit.
Alongside Portal-themed content, Walmart listed LEGO Dimensions add-ons for Scooby Doo, Jurassic World, The Simpsons, and the LEGO Chimera range. Neither LEGO, publisher Warner Bros. or Walmart have issued any statements regarding the listing.
All of the above has been confirmed thanks to an official LEGO building instruction manual for the Back to the Future add-on set for LEGO Dimensions. You can see it over here (UPDATE 2: the manual has since been removed); towards the end of the very brief manual, a number of photos for other add-on sets are shown.