#1
Would there be any difference in say a 1980s Gibson SG vs a 2010 Gibson SG in sound/tone?
#2
Probably?
But saying that... I wouldnt be surprised if there was a difference in tone between a 1980s Gibson SG vs another 1980s Gibson SG either. All guitars are different in some way.
Things with strings:
Ibanez J.Custom, Prestiges, RG8, SR5 bass etc
LP's, Strat, Tele
Noiseboxes:
ENGL Retro Tube 50
5150 III 50W
Orange Terror Bass
#3
Different models over the years could have different specs, electronics, etc... so yeah it's possible. And wood ages, so that could possibly affect the tone slightly over time (usually in a favorable way, if the guitar has been taken care of). And like Shor said, even models within the same year might have subtle differences, although in my experience that's more of a difference in feel than tone.
Current Gear:
2002 Gibson Les Paul Standard
'57 AVRI Fender Stratocaster
MIJ Fender Jaguar Special HH
Marshall JVM410
Vox AC15 C2
#4
The older the guitar, the sweeter they sound imo. The magnets lose a bit of their magnetic properties over time and the wood ages, all in good favor of the guitar.
Another thing is on older guitars they used different magnets, potting techniques etc than they do nowadays which makes them sound different too.

Models from the same year/period usually don't have too many differences, but sometimes you're unlucky and picked the shitty one from the assembly line.
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#7
As wood ages it tends to produce a better tone, as do magnets (pickups).
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