I'm assuming if the organizers want to add a new discipline it would be added by the IOC the way disciplines are added normally, not through some weird additional sport process.
Going to do my thoughts on all of them:
Ski mountaineering makes a lot of sense, it will already be there in 2026. It feels like a natural addition to the winter Olympics and I would not be surprised if it becomes a permanent addition down the line
Freeride seems like a great candidate. It has a very established world tour and the full support of the FIS. It's probably the most well developed winter sport / discipline that is not currently in the Olympics
Telemark I am mixed on. I enjoy watching it and I'd be happy to have it included, but I wonder if it is perhaps too niche?
Speed skiing is the least interesting sport on this list. It's both incredibly dangerous and incredibly boring. I actually think it has a great chance at being included in 2030 because of where the Olympics are being held, but I don't think it will come back very often
Sled dog racing is a big old no for me
Ice Cross I would be happy to see added. It is relatively well developed and it definitively plays well on TV
3x3 hockey is a no for me, it barely even exists yet
Ice Climbing is a big yes for me, of all the sports not currently in the (pure) winter Olympics this is the one I most want to see added
Cross country running / trail running is actually the single sport I most want to see added in the Winter Olympics. It would allow a ton of non-traditional countries to have a serious involvement in the winter Olympics, and cross country running is a real winter sport when done in wintery conditions
Cyclocross would also be a good fit for the winter Olympics, and I would also like to see it added
If I were picking four out of that list, it would be: Ski mountaineering, cross country running, ice climbing and freeride.
What I expect (from most to least likely): Ski mountaineering, freeride, speed skiing, cross country running