Currently 2 EASA countries require pilot to have a mountain rating to land at a relatively small number of strips, and to land on glaciers. Just because EASA feels the need to standardise the rating and make it pan-European, doesn't mean that any other country has to require pilots to possess it before doing anything that they can do today quite safely without any special rating.
What is rather more bonkers is that today there are a very small number of instructors and examiners who can train for and issue the French and Swiss ratings, and they can do it because they have extremely high levels of local knowledge. When the rating becomes an EASA rating, will all the instructors and examiners be trained by the French and the Swiss, or will pilots all over Europe be able to receive a rating that lets them do stuff that goes way beyond what their instructor or examiner have experienced?