There's a difference between a complete overall and a simple update. How many resources would it burn to turn those 470~ epics into 5XX ones?
I understand and agree with Blizzard's decisions to keep the events the same year after year. While new events would be fun, I would rather have other new things. But not even putting enough work to change some numbers? Really? For the tenth aniversary, are we going to get another piece of mail that mentions that adventurers are in high demand due to the recent coming of Deathwing? It honestly just doesn't make any sense to me. :S