The strange rumors concerning a George R.R. Martin & FromSoftware collaboration from a few months ago are starting to seem legitimate, as comments made by Martin and recent leaks concerning an announcement at E3 2019 suggest that the rumors hold weight.
George R.R. Martin is the author of the A Song of Ice and Fire book series, which was adapted into the Game of Thrones TV show. Martin is supposed to be working on The Winds of Winter (the sixth novel in the series), which is why some people were surprised when rumors started to circulate in March concerning Martin working with FromSoftware on a video game. FromSoftware is the development house best known for games such as Bloodborne and the Dark Souls series, so the dark fantasy tone of their games would gel well with the kind of work that Martin is known for.
The final episode of Game of Thrones has now aired and Martin posted about it on his official blog. Martin discussed the projects he is working on, now that the show has finished and he said that he has consulted on a video game in Japan. This comment seemed to add credence to the FromSoftware rumors, as they are a Japanese development house.
The rumors have not stopped there, as Gematsu is reporting that the collaboration between FromSoftware is legit and will be an open world game set in a realm based on Norse mythology and that it will be announced during Microsoft's E3 2019 conference. The game is being referred to by the acronym of "GR", but other outlets are reporting that the name of the game will be "Great Rune". There is no word yet on whether it will be exclusive to Microsoft platforms.
George R.R. Martin's comment about working on a Japanese video game is the real smoking gun in this situation. It would very much be in character for Martin to dedicate his time to other projects rather than working on The Winds of Winter and it would be hard for any creator to refuse a chance to work with a company like FromSoftware.
The rumors concerning the mysterious "GR" will likely be addressed during Microsoft's E3 2019 press conference, which is due to take place on June 9, 2019.