The two arguments seem to be that Bitcoin will either be replaced by a "better" competitor, or that governments will forbid it as soon as it becomes too success

The two arguments seem to be that Bitcoin will either be replaced by a "better" competitor, or that governments will forbid it as soon as it becomes too successful. Both seem rather improbable to me. The first argument is focused on technological aspects and leaves out other aspects, like the arguments for settling on one "good enough" and trusted store of value. I can see governments regulating mining by regulating the means of energy production, but try getting all nations at a table to form a globally unified front. Some dictators probably like Bitcoin and some democracies might have too many interests/voters against regulating the new market already.