Yeah, I also think that lack of manpower is the main reason rather than some shady business with our data. I highly doubt that they prefer to lose the whole european market over adjusting to the GDPR. And the amount of money, needed for this change, probably also depends on how many accounts exists and how much data they collect.
While it is inconvenient for the developers and businesses, you do get the rights to your collected data.
As far as I know , we should be still able to play the game from the 25th onwards until a new update is released to the store, but we will have trouble buying seeds, as already mentioned.
The change on iOS is quite simple, I suggest creating a completely new account, as it's more difficult with an existing balance:
Log out of your current account.
Click on any free app and try to download it (this way you can avoid/skip a payment method for the new country)
Choose to create a new ID.
Pick your new country (any country outside of Europe should be fine for this game, but obviously USA, Australia, S.Korea or Japan are recommended options).
Complete the registration (for the address: you can just put anything there, you'll most likely don't need it)
Now you can go download ET and you might aswell check out the new store.
When you're done, you can change back to your normal account, but you need to keep the login info for the new account, especially the password. You'll be able to update the app while logged in with your normal account, but the appstore will ask for the password of the new account.
Unfortunately I haven't found a way to change the country on Google Play, yet, without involving the use of credit cards and/or other payment methods. But I'll do checkout the app @kokoryuu has mentioned. So I'll have to wait and see how it effects the game from May 25 on and go from there.