Uncharted has a game coming out soon.
The purpose of the remaster is to get people into the uncharted franchise, to increase the sales potential of the new game coming out. It will likely be bundled, "forcing" new adopters to give it a try.
There isn't a new God of War yet. If I guess we'll see a GoW sometime in either holiday 2016 or early 2017, then you'll see a GoW remaster bundle as well. In fact, if you ever hear about a new GoW remaster bundle of all the games, you can make a lifetime ban bet that GoW ps4 will be announced shortly afterwards.
EDIT: remasters and cameos are marketing tools, as well as income potential. Look how Super smash brothers handles it. They have a game come out, they put the characters in smash. When they want to add attention to a specific title coming out in the future, they'll release the character for smash. It's kind of the same thing as goes with psabr. Old characters showed up, and new titles featuring those characters were announced shortly after.
