As long as there remain viable open-source browsers there will be forks allowing ad-blocking.
The only danger is Google switching Chrome to closed source and adding lots of complex extensions that get widely adopted faster than they can be reverse engineered, but this seems an unlikely scenario.
The other danger would be general purpose computers or smartphones no longer available, but that also seems unlikely.
The final and most plausible danger is different and it is advertisers switching to ads that cannot be reliably distinguished from the rest of the page (currently it seems they don't do it because that removes any direct access to analytics by the advertiser and thus requires them to trust websites and they don't trust them).
The only danger is Google switching Chrome to closed source and adding lots of complex extensions that get widely adopted faster than they can be reverse engineered, but this seems an unlikely scenario.
The other danger would be general purpose computers or smartphones no longer available, but that also seems unlikely.
The final and most plausible danger is different and it is advertisers switching to ads that cannot be reliably distinguished from the rest of the page (currently it seems they don't do it because that removes any direct access to analytics by the advertiser and thus requires them to trust websites and they don't trust them).