How many games nowadays proposes a 400 billion systems galaxy, planetary landings, real scale ojects and star systems?
This may be the only game to make that bold choice. i'd say let them try.
This is what i've been waiting for so long, i'm not sure i would have backed it if it was any less. i dont care between 100 or 400 billions, as long as it is trying to get closer to the real thing i'm in.
But i dont see the point in making it smaller. It will be hard to leave the inhabited region anyway, most players will be there or forced to stay somewhat close to it. Explorers will try to go further, but they'll need to equip their ships, organize themselves and take a lot of risks. it's not like everyone will be at the other edge of the galaxy in the next couple of week after release. though i'm sure some will have already tried, and failed.
we may not find a lot of players because of the size? nice

I find that better like this than to simply play solo.
And when events occur many players will probably get the info and try to get there, so it may not be that hard if you know where to look.
And if they can procedurally generate 10 million systems properly, then they can do it just as well with 400 billions or 1 billion billion, that's maybe simplistic but it's probably just a variable to change at that point, at least not much to change.