The foundation doesn't add anything because they don't write the clients. The foundation does research and gives grants using its resources to fund specific areas and fund related infrastructure. The next upgrade and what it includes is agreed by the various open source clients and is enforced by the validators when they decide to upgrade and implement the changes.

Besides that important clarification, validators are already receiving income for their efforts. The tips and MEV are already flowing to their wallets as we speak, it's only the issuance that is locked. The particular change required to unlock funds is rather trivial and can be implemented on your own even if you wanted to. But doing so without a large consensus of validators would fork you out of the main chain and those unlocked coins could be rather useless, this should show the delicate balance that decentralized consensus involves.