We designed it in a way that we wouldn't ever have to adjust the percentage of block rewards and they cannot be adjusted without a protocol change. (A hard fork, so every node would have to upgrade).
Can I apply for joining Bitcoin 2 signature campaign today?
I knew that the campaign implemented months ago, but have not known whether it has been joinable or not.
The bounty finished a bit over a month ago so now the people who still wear a Bitcoin 2 signature do it without further payments. You're welcome to do it of course.