Well, as you get more and more points, more and more points will get taken away, thus making it harder to make up that deficit every season. Say you end up with 1400 points and are promoted to Platinum. You'll start the next season at 1120, needing over 200 points to move up.

Now, back when everyone was matched with people from their own division, this would also make things more difficult, as you would be playing tougher and tougher teams. But they seem to have changed this, which in my opinion breaks the system. So we'll see.