One of the design goals for Exonaut was to not get caught in the "expansion for only high-level players" content trap. Many games do this and while you may be serving the most active and most vocal players, you will be serving a minority of your players. This is why Project Exonaut is set up so we can add new content to players at any level, even unregistered players.
So what percentage of players would we be serving with a straight rise to the level cap? Here is the data from the first couple of months of play.
Here is the breakdown as of this month (August).
You can see a few more percentage points creeping up into the higher ranks but the vast majority (89%) still play in the 1st two ranks. Let's assume we don't take rank 1 (Rookie) player very seriously. They are just testing the waters and are not dedicated players. Let's just look at players rank 2 (Pilot) and higher.
Even if we throw out the Rookie players, the lowers ranks make such a huge percentage of the population. Level 10-20 make up 75% of our active player base of players above level 10.
Don't Miss an Opportunity
High level players are obviously the most dedicated players and should be served new content. However, if you can add content for any level of player, your entire player population has a reason to come back to your game when you have an expansion. Your content plans and game structure should serve your dedicated players and also work to convert the occasional dabblers to hardcore fans.