It was on sale for 4 hours, then it mysteriously disappeared, and everyone acted like it was never supposed to be on sale. My guess is that instead of selling it for $10, MS last minute offered up GwG money and it proved a better option.
It won't ever be Ryse, solely because of how huge the file size is for that game. Microsoft doesn't want to waste resources and money on thousands of people downloading a 50 GB game. If you want to make a good guess towards what a potential free game could be your first step should be to dismiss any game over 20 GB. Microsoft also wants to keep your hard dives as minimally filled with free games so that you have more room to download purchased games.
Dead rising 3 is 35 GB, so that one is unlikely to go free as well. Along with Forza 5 at 40 GB, that one isn't ever going to happen either.
Edit: Out of every free game with gold given away the largest has been D4 at ~ 9GB and the second largest was Crimson Dragon at ~ 7 GB, so I believe my theory holds. On Xbox 360 the free games with gold never got past 7 GB in size with Halo Reach at ~ 7 GB and Witcher 2 at ~ 7 GB.
A game like Styx Master of Shadows is likely to go free with it being only 6.48 GB on the xbox one, and it selling for only $7 during the sale. Don't expect it in March but do expect it in the coming months.
I think TR is guaranteed before ROTR releases, because it was made free with PS+ for PS3 too so it's definitely a possibility. The only thing I'm not sure on is whether it'll be for 360 or xbox one, hopefully xbox one.