I'm still going to be really pissed off if google do successfully kill F-droid though.
I don't think Google has any intention or desire to kill F-droid -- and here I really understand the situation quite deeply from my decade in Android Security. I worked on platform security, not the anti-malware team, but I knew a lot of the core anti-malware guys and talked to them regularly. I was the twelfth engineer to join the Android Security team back when one small team was responsible for all of it (platform, anti-malware and offensive/red-team), so I knew the anti-malware guys (all three of them!) well back then. The team later split and the anti-malware group grew to dozens, then hundreds of engineers, but my old colleagues were (and are) still involved.
What you're referring to is the developer registration requirements, and those absolutely are another example of Google trying to stop abuse that hurts users, and trying to do it in the least-invasive way possible. The problem is that there is a massive ecosystem of malware out there. Google spends incredible sums of money fighting it, but in the armor v warhead battle, the armor is perpetually behind.
In recent years it's gotten a lot worse, and the old techniques (static and dynamic analysis) are no longer working because the malware construction tools have gotten so good that the malware authors are incredibly agile. When the anti-malware team identifies a malicious app in the ecosystem they have the tools to shut it down, but the authors can replace it in hours, maybe minutes, with a new version that can't be identified. This isn't because the team's malware-identification tools are lousy, in fact they're incredibly sophisticated.
I'm not sure how much of the cat-and-mouse game I should describe here. Both legally and morally it's unclear to me how much I can safely say about the details of what Google does to detect malware and what malware authors do to counter it, so I won't say much. I'll just say that it's a very complicated and subtle technical battle... and Google is losing. Not on the Play store, because they have a non-technical advantage there: Developers have to identify themselves and pay a fee. Those requirements mean that when malware is identified, Google can not only shut down the malware, but can also block the malware author. The author can get another ID and pay another fee, so this defense is circumventable... but the circumvention is hard to scale.
What Google is trying to do is to apply this same highly-effective non-technical defense to the rest of the Android app ecosystem. Not because the fees mean anything, and not because Google objects to the existence of other Play stores, but because it's a simple and extremely effective way to break the business model of Big Malware.
Will it stop all malware? Obviously not. But it will make malware hard to scale and that fact alone will destroy the malware business model, and with the financial incentive removed, the sophisticated malware industry will die. This will actually benefit the Play store, too, because less sophisticated malware is easier to identify and kill.
If Google succeeds at this, it shouldn't kill F-Droid. It will just mean that someone, somewhere, in addition to spending their time on building open source apps and packaging them for distribution, will also have to give $25 to Google, and send their ID. Unless Google can work out a different way to handle F-Droid... and that seems very feasible! F-Droid's requirement that source code be available is a really good defense against malware, not so much because of "many eyes" as because people would be very skeptical of any open source code that does the obviously weird shit that malware does to evade Google's detection schemes.
Bottom line, I don't think F-Droid is at risk, and I don't know anyone in Android who even wants to eliminate it. Well, no one in a decisionmaking position, anyway. I do know a few Android engineers (in the security team) who sincerely believe that Apple's walled garden model is superior because it makes security a lot easier. But that's very much a minority view. 99% of Android engineers want their platform to be open.