Central Asia might embrace Bitcoin for washing trade with Russia and especially to give innocent Russian Citizens the ability to get out of their worthless Rubels. The long border is basically impossible to control and officials are corrupt anyways. Buying a little jewelry in Moscow and selling it for Bitcoin in Azerbaijan or Turkmenistan is what I personally would do.

Subsaharan Africa could also benefit from it. The goverment currencies there are not very trusted anyway.

Other Latin American countries for the same reason as ElSalvador. I suspect that other counties leaders there are already thinking about it but are just hesitant and want to watch how El Salvador plays out. Especially with the volatility of this month.

I don't think any more countries will make it legal tender. Rather a country may see its financial system break down and the people resorting to bitcoin or something similar instead.

Probably another country that doesn't have it's own currency. It would be too hard of a sell to a country that has one. From learning about the CFA system, it seems like even worse of a deal than being dollarized, so I'm guessing another country under the Colonial Franc. I'd guess not until the price recovers a bit though.