World of Color - Celebrate has gotten rather tepid reviews. It does not seem to be as well-liked as
Disneyland Forever and Paint the Night. I wouldn't be surprised if that disappears before anything else.
While there is no official end date for any of the offerings (and, yes, it is a subject that has come up a lot on this forum!) and some of them will likely continue on indefinitely, it is important to note that it is unlikely that the current "all 60th, all the time" schedule will continue on into next year, and especially beyond 2016.
For example, right now and probably through the end of the year, the only fireworks happening are Disneyland Forever, with the exception of Mickey's Halloween Party nights -- which will have Halloween Screams fireworks. There will almost certainly be no holiday season-specific fireworks this year (which is also what happened in 2005, during the 50th anniversary). I would expect that at some point in the future, Disneyland Forever will be scaled back so that the holiday fireworks can be reintegrated into the season, and also scaled back from a nightly schedule (which is what is happening this year) to a "regular" fireworks schedule (which means, during the off season the fireworks would not be nightly). So, Disneyland Forever will probably continue on into 2016, but maybe at a reduced schedule as compared to what is happening now.
Paint the Night may eventually be scaled back too -- isn't it currently running 2 times each night? It could be scaled back to only once per night by next year.
As for the hotels, the GCH rooms are rather cramped, in my opinion. There's not a lot of floor space to set things down. The public areas of the GCH are wonderful - the lobby is a great place to hang out with a drink in hand, and Storytellers Café is a decent place to eat. The whole vibe of the GCH is that of "rustic elegance." It almost seems like a high end ski lodge in the mountains.
The Disneyland Hotel's rooms are more spacious, and there are many more "classic" Disney touches around the property -- character topiaries, teacup chairs in the lobby of the Fantasy Tower, Mary Blair-inspired art, retro collages, etc. Tangaroa Terrace is a good counter service location, and Trader Sam's is very popular as well.