Will players claiming the "best" plots of land on day one be an issue?
TL;DRDay-one land claiming shouldn't be an issue, because there is enormous land across many planets and moons, more coming with new systems, and players value plots for different reasons.
No. Due to the billions of square kilometres of available land over many planets and moons and of course as new Star Systems are introduced and explored, all players will have the ability to find and claim new "hot spots" throughout the lifetime of the game. Also, every player can have their own reason for what could be the 'best' piece of land, while some may judge a plot of land based on the type and quantity of natural resources that it contains, others might be looking for proximity to trade routes, and others could simply look for a quiet spot with a beautiful vista. This - combined with the fact that there's an enormous amount of real estate available - means that prospecting and the purchase of land are two pieces of a supply-and-demand equation governing how rapidly land of a distinct perceived value will come on the market.