Doesn't the same also partially hold for Firefox and Chrome, though?
They wouldn't start charging for Chrome, as that's not their business model, but they might move part of their development out of (open source) Chromium and into (closed source) Chrome or further curtail extensions (e.g. adblockers) etc.
Google has done that with Android, moving more APIs and features from the open-source AOSP core to the closed-source Google Play Services library. Google can then control which Android partners get permission to ship Google Play Services for a full-featured Android experience.
As more browsers move to a Chromium base, Google might have a similar push to move more of Google's value-add out of the open-source Chromium core to the closed-source Chrome product.
No. Firefox vs Chrome is a completely different comparison than Wikipedia vs Encyclopedia Britannica.
The first two are browsers; software, the second two are stores of knowledge.
Browsers have been free for the longest time now, they are a commodity; the 'for pay' browser market died a long time ago. Possibly that was a mistake but that's where we are now and the parties that supply browers (Mozilla, Apple, Microsoft, Google to name the bulk) all try to win marketshare because they benefit from having more users. Putting up a barrier will automatically play into the hands of the opponents.
Wikipedia is a free and much larger alternative to EB, which historically was very expensive. If Wikipedia goes away there is no longer any incentive for EB to have a free tier, which is the one thing they can do to erode support for Wikipedia a little bit.
I'm not disagreeing that (in these scenarios) EB would probably become paid-for, while Chrome never would. I'm just arguing that Chrome would become even more privacy- and user-unfriendly, which is the approximate equivalent of EB putting up paywalls. (Is paying with your attention and privacy better or worse than paying directly with money?)
Apple would continue offering a relatively privacy-friendly alternative — but would require you to switch OS to use it; Microsoft might fork Chromium, but I fear that they'd only pay lip-service to privacy.
Obviously these analyses are complicated by the fact that in both cases the forces that helped create Wikipedia/Firefox wouldn't disappear. If Wikimedia died, then people would put up their Wikipedia dumps online in their own MediaWiki instances. If Mozilla died, then people would either try to keep Firefox alive or try to maintain a set of privacy patches on Chromium. How successful they'd be is another matter...
