One other thing to note about the Social Network UHD: it contains an R-rated version of the film. It's the exact same cut, but the audio track retains an extra f-bomb that was previously dubbed over to get a PG-13.
It's been a few months since I watched The Social Network on UHD, and I didn't do a back-to-back comparison with the Blu-Ray. My recalled impression, however, is that it only offered marginal improvement over the Blu-ray. I love the film, but it was an early Red production, and it still looks...
Both titles have been rumored for months. The Bits even posted in January that a Panic Room announcement was imminent, but nothing came of it. I wouldn't be surprised if both titles are being held for release so they can tie-in with The Killer later this year...
I also think Gone Girl is available in 4K via streaming. It's a Fox title, and I believe the rights were acquired by Disney in the merger. I don't hold out much hope that Disney will give it a disc release given their focus on streaming. Same with Fight Club, although that may have a better...