This is the same idea as waiting to buy a computer until they're faster, on the assumption that the faster computer will give you the answer sooner. About twenty years ago, this idea was quantified and published in the paper "The Effects of Moore's Law and Slacking on Large Computations", which you can read here:

https://archive.org/details/arxiv-astro-ph9912202

Country X will have 40 years of experience of actually being in space and might learn much more valuable knowledge than the theoretical advances made by country Y.

You're assuming the 60 years after Country X's starship is launched is going to be a period of progress.

If it's a period of collapse, perhaps complete collapse, humanity will have lost an opportunity by delaying the launch.

> It has been argued that an interstellar mission that cannot be completed within 50 years should not be started at all. Instead, assuming that a civilization is still on an increasing curve of propulsion system velocity and not yet having reached the limit, the resources should be invested in designing a better propulsion system. This is because a slow spacecraft would probably be passed by another mission sent later with more advanced propulsion (the incessant obsolescence postulate).

https://en.wikipedia.org/wiki/Interstellar_travel#Wait_calcu...

There is a fair amount of thought that has gone in to that, often referred to as the Wait Calculation.

An interesting example was "Interstellar Travel - The Wait Calculation and the Incentive Trap of Progress"¹, which somehow isn't on libgen [yet?].

1. http://www.jbis.org.uk/paper.php?p=2006.59.239 - The incentive trap of linking to a £5 download for fifteen year old paper is another paper entirely.

The "incentive trap" has also been referred to as the "incessant obsolescence postulate", in this paper from 2011 titled "Energy, incessant obsolescence, and the first interstellar missions":

https://arxiv.org/abs/1101.1066

The author also uploaded that paper to Researchgate, where it's available for free:

https://www.researchgate.net/publication/260275150_Interstel...

(edit: I presume the downvotes are for linking to Researchgate? I know they're not held in high regard like Arxiv, they're more like a sleazy Linkedin for academics, but if there's valuable content there why not use it?)

Are you asking for a value judgment? Or what exactly is your question? This can happen for example in some games like Master of Orion. You send a ship to the border, and before it gets there, you've already researched, built, and deployed a faster version. Sometimes it changes things, sometimes it doesn't. If your sole purpose is simply to arrive then it hasn't changed a thing. If you are planning to fight aliens when you get there, however...

This is a plot point in various SF works.

For example, in the Honor Harrington books by David Weber, the Manticore system colonists traveled to their target a couple hundred years in hibernation. But as it was likely propulsion technology will advance before they reach their destination, they also left part of their money in a trust fund back on Earth, to make sure the Manticore system won't get squatted in the meantime.

This proved to be a sound idea, as practical FTL drives have been invented after the colony ship has departed and they have been greeted by the Manticore Trust navy upon arrival, that has secured the system a couple years earlier, arriving by the newfangled hyper drive. :)

Very nice. Alastair Reynolds touches on this concept as well in Chasm City.

This idea is in the game Elite Dangerous, and you can go and look at them: https://elite-dangerous.fandom.com/wiki/Generation_Ship

The lore is quite amusing and poignant. Many of them met a sad end in one way or another, reminiscent of Fallout.