Hey I’m just responding over here again because I did not mean to derail the announcement post with this discussion.
It’s exactly this. The current universe, and thus the current 50 planets, would be at full capacity at roughly 4250 concurrent players. That means literally no player could even access a single portal leading to a public world.
So regardless of the numbers that could theoretically be supported on sovereigns, etc… we don’t currently have any in-game or social infrastructure to support this, and especially as pop-up growth.
Yes we can have sovereign only, or even partly sovereign portal networks that create and bridge the networks connecting things now but, none of that exists, and it’s not exactly simple to create in a rush.
Lots of people would be working on it, I’m sure. But also a lot of people would just be stuck. Unable to leave their planet (or probably do much) until some people at least just log off.
And some of those people won’t probably be logging back in 
As also discussed here, there are some issues with the current systems in place (whether or not they’re on autopilot) that can make it a real mixed bag how someone’s early gameplay goes, just based on when they log in to a rapidly growing universe.
A player that spawns into a planet that auto-generated today is basically spawning into 2018 boundless without even portal seekers around yet.