Not all extensions are going to be ported. Period.
That's right. I never claimed otherwise. The popular extensions, and the ones mentioned by the OP, however, will be ported. The OP's favorite add-ons will continue to work. This change affects him in no way.
You know, the add-ons that people actually use. UBlock Origin, NoScript, etc. are being ported. Hence, this change will affect almost no one.
For those (very few) devs posting nonsense about how this comes as a total shock, they've had almost two full years to prepare, and they still have the remainder of this year! They've even had ample opportunity to work with Mozilla to shape the new API.
So, no, not every add-on will be ported. Of course, considering the incredibly long time they've had to make the change, I don't think users are missing much by losing what are very likely to be low-quality add-ons with little to no support.