Technically, fiat is only needed as cash
If we take electronic payments and assume that Bitcoin could be scaled up efficiently and effectively (which is a big assume, to be honest), I see nothing that could prevent Bitcoin from substituting fiat. In fact, on a world scale, Bitcoin would beat fiat money hands down any day, since the transactions are propagated almost instantly across the world (maybe, a few seconds at most) and the confirmation times of ten minutes (remember, Bitcoin has been scaled up to the level of adoption) are also almost instant in comparison with wire transfers that take up to a few days, especially if you send money from one country to another on the other side of the planet
If everything turns around the dollar as you say, shouldn't we then consider, for example, Swiss franc and Euro as alternative currencies too, in the sense you mean it? If we compare economies of the US and the EU, they are pretty close, so there is no reason to think the Euro is an alternative currency to the US dollar since it could be claimed in absolutely the same manner and to the same degree that the US dollar is an alternative currency to the Euro. In respect to the Swiss franc, it is thought as a more stable currency than the dollar itself, therefore there is hardly any plausible reason either to think that it somehow depends on the latter
That's very true. Altcoins are no more valid or invalid than Bitcoin. The only difference is Bitcoin has been around longer. Angel investors spent money building infrastructure around Bitcoin because it was new and they were looking for something cutting edge to invest in hoping for that "Mark Zuckerberg" success someday. They could just as easily have invested in Litecoin and it would be the most recognized coin today. If Litecoin were around at the time and Ross Ulbricht used it for Silk Road purchases then Litecoin would be on top.
Well, somehow I didn't expect that you would agree with me
I agree with the truth regardless of whether it favors Bitcoin or it's against it. What you said is the truth.