There's already not going to be a Christmas parade (and I agree -- there will be no garland hanging over Main Street), not going to be holiday fireworks and not going to be a holiday World of Color. There is also likely not going to be a "Winter Castle" as we have come to know it, with the icicle lights -- even though I like the icicle lights better than what is currently on the Castle.
If Disney decides to not decorate IASW's façade in colored lights -- even though I am pretty sure it was somewhat decorated during the 50th anniversary year -- that is just too much 'loss' on the holiday front. That is the turning point at which the 60th anniversary will begin to annoy me, because it will be interfering too much with the holidays.

I mean, it's lovely that such a big deal is being made of the Diamond Anniversary, and I realize that Disney put a lot of money into hyping it, promoting it and getting the new entertainment and all of that, but their holiday season is amazing. Holidays at
Disneyland Resort are known for being amazing and immersive, and there are actually some people (who don't follow social media or discussion boards) who will go to the parks wanting a holiday experience. Those folks won't care that much about the 60th. There has to be a good balance of "60th" and holidays, and removing the famous colored lights from the façade of IASWH will be very disappointing -- even IF the star returns to the top of the Matterhorn, it won't make up for the loss of colored lights on the façade!
Halloween's décor is minimal in comparison to the holiday season, but I can't see why they wouldn't put the 300 pumpkins on Main Street, along with the orange bunting on the facades, as usual. The décor in Frontierland should be the same as it is every Halloween Time.
Then again, if MHP -- for some reason -- is not happening in DL this year and is happening in DCA, they could tone down Halloween in DL.