SNP won't disappear if Scotland ever becomes independent .. Farage didn't disappear after Brexit, Putin didn't disappear after being elected Russian leader. The SNP are tribal nationalists who claim to be the only party of their tribe. They will apply the 'not a real Scot' fallacy to all others.
You’ve conflated two different things. Farage focusses on personality politics, forever looking for a new bandwagon to jump on. The SNP are the exact opposite of tribal nationalists like Farage, and once independence has been achieved a new political landscape in Scotland will form.
Of course they are .. Watch this space.