I agree that a solitary elixir of discovery is weak.
However, I don't think it makes sense to do what you are suggesting - business wise.
If they afforded those who have already purchased the expansions a discount on upgrading the tier - that would make more sense. But it doesn't fit with the theme of "free gifts for Year of the Dragon" if you need to fork out anything.
So really, they should have just offered a little more than the elixir. Or multiple elixirs. Or a bag with goodies. Or an Otto's box. I don't even like or use them - but that would appease a lot of people I'm sure.
Well, this downtime is quite lengthy. Maybe that will give them enough time to come up with something