Lets hope they stay independent and never get acquired by Google or any other large tech company. You can imagine a web where SSL issuance is used as a tool to censor websites. I think most browsers have been made to make standard http sites look malicious to normal users.
If Google wants to censor your website, they have a variety of other, more effective methods, like by adding it to their safe browsing blacklist, which is also used in many Firefox installs.
As someone else mentioned, it's a non-profit, so I guess it's not technically possible to get acquired.
But I personally believe that the people behind LetsEncrypt genuinely care about the mission and will never sell out for their personal benefit.
If there was a list of organizations that bring the most impactful things to tech per each dollar received in donations and per each employee, ISRG will be up there at the top.
They're a nonprofit - so they can't be acquired like a typical for-profit company. They could in theory sell some assets but it'd be very convoluted if they were the core assets -- per US tax law, nonprofit assets must remain in the nonprofit world, so there's no risk of any tech company ruining them.