Im gonna be honest here,
Halo is and always will be my favourite game of all time, but I really can't see something like a 20th anniversary or a 30th anniversary. The reason 343i own Halo now is because:
A) Bungie wanted to become independent
Microsoft wanted Halo to turn all CoD-ish and have at least one game come out annualy (at least that's what I have heard)
So if a Halo game is going to come out every year, great in the short term but in the long term, I really cannot see how much more this universe can be stretched. But then I really do admire your creative and inspirational Ideas. Prehaps YOU should be the guy at the Halo drawing board. Coming up with all these game ideas. I haven't read the books but if this is where the franchise is going and you have these ideas. Im sure to get every one.
Overall, Brilliant! good work