With regards to whether we can merge with some AIs, the bird-plane analogy is completely misplaced here. Flying is a singular function, so of course it wouldn't make sense that you'd do it better by merging 2 totally different engineering schemes to accomplish the one same function. But that's as different to intelligence as you could possibly get, the amount of functions intelligence has is practically infinite, and so merging makes complete sense there. In fact, we already know that's what the brain does. We have different brain regions specialized in different functions, all collaborating together to yield our overall intelligence. And also, we've already added external functions to it by using calculators, phones, computers, etc. There's no reason why that trend couldn't continue. It also doesn't make sense to view the whole of AI progress as one exclusive either or thing: "Either it's a consumer product or it's a new species". Everything we know about how technology progresses, and how AI in particular does right now, points to the fact that it will be both and everything in between. There's no doubt we'll keep developing tons of AIs of many, many different types. Some will be more attuned to cooperate more and more closely with us, functionally merging at some point with the aid of more advanced technology. In general, I disagree with your arguments of why this is a necessary evolutionary event leading to human extinction, it would be too much to get into each argument, let's just say to me you seem to frame evolution way too much as some sort of elimination rounds tournament. The best point you made in all this is about being able to replicate, that's really what it's all about, not necessarily only about being the best competitor, and especially having to be the #1. Anyways at least we should stop saying humans can't further progress and improve themselves by merging with the technology they develop, including AIs, that just doesn't many any sense at all.
I believe that we really are in the midst of one of those very rare phase changes and none of us can truly see what is on the other side. Almost all of the prognosticators are leaning on the "tomorrow will be much like today" mode of thought. They are likely wrong.
