It depends on timing. When you make the contribution, there is a time window for voting. If I remember well, that's 7 days. This is configurable, but I'm pretty sure it's 7d right now (https://www.steem.center/index.php?title=Rewards:Formulas#Worth_of_a_vote)
At 7th day after posting, the underlying platform will calculate the final reward and from now on any further changes are ignored. After that, it's past, and almost nothing can have any retro-active affect. The amount was awarded and it's locked. However, if the contribution has been 'flagged' (spam, abuse, etc), the reward may be cancelled even after being paid out, so it's not totally frozen.
If the delegation returns after 7th day, then it will not have an effect.
This should be clear, but there's still a small question, how are changes occurring during the 7d time window accounted for. For example, say, if I upvoted you now, then 5d later I managed to become the largest whale on Steem, will you get the reward according to my current status when I performed the vote, or according to my status at the time of reward calculation?
I had no idea, but I found this a bit-old post: https://steemit.com/steemit/@shenanigator/updated-steemit-faq-part-4-payouts and while some of the bits may be already outdated, there's a very important note:
That weight is a function not only of the rshares they contributed to the post with their upvote (which is itself proportional to the product of their chosen voting weight percentage and the total amount of VESTS they had at the time of the upvote)
The VESTS is the SteemPower, so it clearly shows that the voter's current SteemPower is recorded at the time of voting, so I say, when I become a whale tomorrow, that's irrelevant to my voting I do today and the same applies to utopian: if utopian votes your contribution up before delegation returns, it's done, and even if the delegation returns before 7th day, utopian's SP was already recorded and that will not change the calculation.
So that's how it works, very clear to understand, thanks. You give pretty neat examples. Now I have a question that, is this not going to be like a little unfair for contributors until that amount of time? Just a question.
Well.. it depends on what you consider unfair. Utopian will stil work, just with less punch. That does not mean any rules are changed. I also don't think that Steem Inc is obligated in any way to support Utopian. Considering that and other things, one may consider unfair that they do support Utopian and not all other activities :) But, jokes aside, it'd be somwhat unfair if they didn't notify about that and if we were meant to contribute solely for profit. They did, and we are not, so from my point of view it's as fair as it could be. They even stated when they'll delegate SP again, so if someone is really keen on the profit, they can just wait that week and post afterwards. Keep in mind that there is no guarantee that utopian will vote-up on that contribution, even if the contribution is fine&dandy, there's still no guarantee..
Btw. I don't really know what account Steem Inc uses, and how much they did delegate, but I just looked at utopian-io delegators and amounts at https://helloacm.com/tools/steemit/delegators/ (or https://join.utopian.io/sponsors/) and utopian-io still has a tremendous power.. If they upvote a post, that will be significant, even without Steem Inc power to back them.
That's quite the info, thanks.