One of the appeals of salsa indeed was it is a fast dance when compared to others. That is why people danced it and liked it.Salsa is mostly a fast dance, and in the 2010s many dancers told me it's too fast for them and so they switched to slower bachata / kizomba, where they often stand still and don't even move their legs anymore. The music taste in general was in favor for slower music the last years. The same in WCS, the music they dance to has strongly slowed down compared to videos from the 90s. Even in salsa we had the EU on2 movement preferring slower moves to slower music.
So for making salsa attractive again you need people liking faster music and dancing faster again. There is a chance because after many years of preference of slow dancing / slow music the preference might change again. But fashions are hard to predict.
EU festival scene is too small to impact salsa dancing trend outside of Europe. Within Europe too, it hardly impacts say Cuban salsa scene.
I don’t think there is any EU on2 movement. When I actively danced, only a small number were dancing slowed down new age salsa.
Each scene develops its own vernacular of salsa dancing. When people shared the same space dancing the ideas and movements get borrowed and converge. EU festival scene can be considered an equivalent of city level scene. Certain music choices, dancing style, etc evolve and converge. It is like people from different places speaking a language with mild regional accent.
It is hard to tell whether (at least) in the USA salsa dancing got diffused, stagnated, or stopped growing. Because we are only talking about the studio trained dancers. The scene is a lot bigger when you consider casual dancers who do not behave like studio trained dancers.
Locally I went to two socials in the past seven days. After a long gap. One is relatively new which started a couple of years back. The other is probably the oldest running social. Both cater to dancers who learnt salsa in salsa school or studios. The first one is not on2 specific but is dominated by on2 dancers. The oldest running one was always on2 space since on1 dancing was far more popular.
In both socials; there were may new faces I had never seen before. Each social had different new faces. Probably because they were in different parts of the metro region. The weather was also bad past seven day with heavy downpour. One in the city and other in the nearby smaller city. Public transport makes it difficult for city folks to go to neighbouring city without using uber for connection between public transport node and studio location. That social still follows traditional timing of 10.30pm to 2am. There are several three or four competing places around the metro area that you could go dancing on the same night. I exchanged notes with regulars and everyone said the same thing. The ratio was something like 15% regulars and 85% new faces. There were between 70 to 100 dancers at each location. At the traditionally on2 location, the skill level of new faces was relatively better. Like those dancing for a year or two. One of my friends speculated whether it was bass bunny effect. My counter was most of these new faces must have started taking classes a year or two earlier. If this trend continues locally, then a lot of fresh blood is entering the scene at the socials I go to. Let’s see where the things are in six months.