What if bitcoin will be made as the official cryptocurrency, promoted and regulated by the government, what will be the effect to other cryptocurrencies? Is there a chance that others will be banned? How do you if will affect the bitcoin price? Will it be a negative impact on bitcoin itself?
I don't think that will ever happen. Bitcoin can, and probably will be considered as an asset and as a currency, since it can be both, but it wont be officially backed by the government, as in "controlled by it". Bitcoin is suppose to be decentralized, and it will remain that way. The only thing governments can do, is to ask for licenses from exchanges, and make citizens pay taxes on bitcoins, as they already do on gold and other stores of value.
I don't think it will have any effects on other crypto. If they are for real, they will be used just like bitcoin, and be regulated the same way.
Just take a look to Japan, and Switzerland, they are good examples of what governments can do to crypto, in order to have a good relation with them. Or even Russia, that right now keep sending different messages to public, but the last information I read about it, is that Moscow Stock Exchange plans on trading cryptocurrencies, so again, this looks like a good way to do regulation.