That won't happen. People will install Chrome, and that's the end of it. Well, not the end of Google, of course, which will now have even more opportinuties to grab your data and sell your privacy.
I'm not sure you're really following. If developers are already jumping through hoops to make their extensions available for safari users, the only way this "will not happen" is if apple makes barriers to entry even worse.
Safari will become irrelevant. Users, some through ignorance, others coerced by incompetent front-end teams ("Safari is the new IE") will switch to Chrome. It will be the end of Safari. There will only be a few extension developers left.
When that happens, please switch to Firefox. It has more extensions than you'll ever need, and it's better for the tech environment and your privacy.
I use Safari as a daily driver because it tends to have a low impact on my machine. Whether Apple has the stomach for competing with Google directly after these changes remains to be seen, Microsoft threw in the towel after all.
