The Xbox Live Gamerscore has always been used as a clear way to determine which one of your friends took gaming to a totally new level. You see somebody who has a Gamerscore of 2,000, while another person has a score of 890,000. Which one is better? You might assume that the person with 890,000 is the better player, but Gamerscore is not now, nor has it ever been, a true indicator of how good somebody is at video games.
Let's say you have a professional Halo 5 player on your friends list. Odds are, they spend all of their time playing Halo 5 and they might have a Gamerscore of 200. Just because it's only 200, it doesn't mean that they're bad at video games. Microsoft is acknowledging this and wants to make a better system to help celebrate more players for different things.
In an interview, Xbox Platform Corporate Vice President Mike Ybarra stated that this rework of the system will "fundamentally change the concept" of achievements. Now, we have no idea what that means exactly, but it should be really interesting to see. Maybe each game will have your stats posted up on your profile page, like your rank, headshot percentage, and overall accuracy for shooters. Games like Rocket League can show your total goals, saves, assists, shooting percentage, and season rank.
They have the chance to do some really great stuff here and I'm sure they won't disappoint. There is no date being put in place yet for the update, so we're probably going to be waiting for a while. It will be applying to the Xbox One and Xbox One X for sure. I'm assuming that the Xbox 360 will be getting a change as well unless Microsoft decides that the console is too old for a redesign. If there are any last minute achievements you want to make sure you get, I would probably get moving right now before your chances might disappear forever.