Some states in US allow you to take a photo of your ballot. This means they can already do the things you mention. But they don't, because it is illegal. It will continue to remain illegal.
If you are very worried about such a scenario, verify that your vote is on the blockchain, then destroy your receipt.
The fact that a receipt exists means that you can be pressured to provide it. If my boss wants me to vote for pro-business-owner anti-union candidates, he's not going to take "Yeah I promise I voted for your guy, but I destroyed my receipt" for an answer.
I don't really buy "it's illegal" as a counterargument. There are a lot of things employers pressure their employees to do that are illegal, but the employees don't really have the ability to do anything about it, because they're taking a risk on the legal system working out for them, and in the meantime they'll probably lose their job and be known as an employee who litigates against their employers. As a wise man once said, if you're a single-digit millionaire, you have no effective access to our legal system.
If you are very worried about such a scenario, verify that your vote is on the blockchain, then destroy your receipt.