We definitely can't change private polls to public for privacy reasons. It's not even an option for us in the software to do that.
Sorry, I guess I didn't explain the question properly.
The poll is Public.
And it works for everyone as Public, before he/she votes.
But after he/she votes, then the poll in not Public to that person any more. But it is still Public to everyone who hasn't voted yet.
The change would be to allow the Public polls to remain Public to everyone after they vote.
You can do a quick test to see what I mean. Create a Public poll. Watch it a bit as people vote (but don't vote yourself, yet.) You will see everyone's name and how they voted. Then go ahead and vote. The name information will be gone. Only the numbers appear for you.