How disappointed would you be?

I wouldn't be disappointed at anything. ¯_(ツ)_/¯. The way I look at these events is as a bonus, but not a requirement. (Like you said most these events are quick money grabs for Niantic) I'm not going to hold off on evolving anything I need in anticipation of some event that may or may not happen. Most player spent way too much time trying to decipher what that worker mean when he made that cryptic statement. In short for me it's not an enjoyable way to play the game. lol

They could do it with half price candy evolutions, instead of straight up double XP. The resulting XP would be the same as dbl xp from a specific number of evolves, but it would require twice as many evolutions...so twice as long to get it - so people use more eggs.
Then they half price eggs, and people see it as a bonus and spend extra to make use of the 'half price candy evolves'.

So it is dbl XP for all your evolves - but they sold eggs, at half price, to people who needed twice as many.

The bonus, players get 2 shots at evolving a good moveset, to reset their lineup after the recent reshuffle.

Good for money
Results in dbl XP
Good PR.

...but that is just what I would do.

EDIT Also extra evolve items from pokestops to encourage evolves and give dbl shot at movesets

My guess is that lucky eggs will last longer during easter and also half distance for hatching eggs (1km, 2.5km and 5km). A lof of people does not even care about xp past level 30 but everyone wants those rare mons with good moveset/iv and 90% of them come from eggs, also this is an incentive for rural players and others that don't have gen1 completed and they need Snorlax, Lapras or Dragonite for example.

All the events that had something related to egg hatches had made me intent to buy extra incubators, at the end I only did it during halloween but just because I had enough coins saved from gyms during the other events, if I had not I would have bought more for sure, even just a round of them to see if I was "lucky".

I think Niantic will focus it more on egg hatches if they are smart, at the end 1 incubator is more expensive than 1 lucky, and you don't need as many lucky eggs even if you do for example 10 mass evolve sessions.

Who knows, I take the events as they come, and I play for today, not for next week, or next month, ya know.

I've been saying this for a while, my guess is double or trip Lucky Egg timers. Hence save your candies.

Don't we already have a lot of people at 30+? and Why did you get you hope up for double xp?. I just don't get it.