Maybe the question is...how much is considered too little change? A game set in the 63rd century where gunpowder-based firearms are still the most common military weapon? A setting 200 years from now that has no nanotechnology? I'm sure that there were people in the 60s who couldn't conceive of not having settlements on Mars in 2005...but we don't.
It depends on the preconceptions of your setting.
There was a great, old hard sci-fi story about how humanity colonized virtually the entire galaxy without FTL and without encountering intelligent alien life...until they did, right at the "end" of the galaxy! The 2 cultures were deeply involved in communications- deciphering languages, techologies, etc. for a while until they discovered...
The aliens weren't aliens- they were actually 2 branches of humanity closing the circle. It had taken so long to explore and colonize the galaxy that the vanguard going "left" and the vanguard going "right" had evolved into seperate, but still human (to themselves, at least), species.
You might have gunpowder weapons predominate in the 63rd century if energy weapons are too expensive or difficult to mass manufacture (think of Firefly/Serenity), or perhaps if a theocracy controls most of the "empire" and has banned energy weapons as "unholy."
In Ben Bova's (utterly awesome) "Planetary" series, nanotechnology has been banned (on Earth) because of certain "industrial accidents" plus cultural phobias whipped up by religious ultraconservatives brought politial pressure to bear upon the government. Even offworld, nano has a mixed rep, and isn't used openly, and only rarely and in certain circumstances.