these predictions remind me of a commercial where a guy asks genie "a million bucks" and genie promptly delivers 1mil male deer/antilopes.
$300K number is irrelevant in 10-20 years because we don't know what it would mean then.
If you say: each bitcon=6667 barrels of oil or each bitcoin=25K movie tickets or each bitcoin=Ferrari FF or Rolls Ghost, then OK
The oil price isn't exactly stable, we don't know what 6667 barrels of oil means in 10-20 years from now either. I'm guessing OP means $300,000, adjusted for inflation, with the same purchasing power as $300,000 today.