Not the richest in the world, but they would gain a good amount of money from it. You can trade based on current USD value.
How much do you think btc would go up if a small country announced it would use it as currency and back their dollars by it? Would it hit $1 trillion market cap then? Maybe? Also at 1 Trillion market cap, it wouldn't be as volatile. What if the leader of that country also invested 1 Million or more in bitcoins? There are many selfish reasons why this could happen? News like this would make the currency skyrocket. What if a country announced it and then a month later said they're not going to do it.
Now what if they used litecoins or another? Would that currency then overtake bitcoin?