I think we are safe here. There is just no way the most popular add-ons of all times would just disappear.
From what I can see, the worst case scenario is that one add-on will have a limited filters amount, so instead of installing one adblock with multiple filters, you will install multiple addblocks, each for a specific filtering.
Also people comparing this with Firefox 57 add-on “Armageddon” are not correct, since as an add-on developer I can see the benefits of Webextension API and I know this was just necessary step towards brighter future 
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Similarly comparing this with Play Store removing adblocks is also not good since Android has no real competition that allows adblocks so they can do whatever they want.