If you read the official announcement for the German language (cited in the wiki article) there it states that SS is the capitalization of ß, but ẞ instead is permitted. So the standard Form is double S.
Question: is there any reason to expect that the double s form will be replaced, or is this a more of a permanent quirk of a language adopting quirks from their neighbors?
Difficult to say. The double s Form has to stay (for small and capital) to not deviate from Swiss German too much (has to stay compatible). Generally older people think capital ẞ is ugly, but maybe this will change over generations. Best bet (for me) is that all ß fall out of favor and Germany goes the Swiss way. Let's talk in 60 years again.
When I first heard about it a few years ago I did indeed think that it was ugly-looking and the whole idea rather pointless.
I've recently re-discovered it, though and somehow this time around actually taken a liking to it, and have smuggled it into a few reports I've had to prepare since then.