5 years ago, almost everyone in this forum would have said that something like GPT-5 "is probably further out than the lifespan of anyone commenting here."

It has been more than 5 years since the release of GPT-3.

GPT-5 is a marginal, incremental improvement over GPT-4. GPT-4 was a moderate, but not groundbreaking, improvement over GPT-3. So, "something like GPT-5" has existed for longer than the timeline you gave.

Let's pretend the above is false for a moment though, and rewind even further. I still think you're wrong. Would people in 2015 have said "AI that can code at the level of a CS college grad is a lifespan away"? I don't think so, no. I think they would have said "That's at least a decade away", anytime pre-2018. Which, sure, maybe they were a couple years off, but if it seemed like that was a decade away in 2015, well, it's been a decade since 2015.

GPT-4 was a massive improvement over GPT-3.5, which was a moderate improvement over GPT-3.

GPT-5 is not that big of a leap, but when you compare it to the original GPT-4, it's also not a marginal improvement.

GPT-2 to 3 was the only really "groundbreaking" one. 3 to 3.5, 3.5 to 4, were all just differences in degree, not in kind.

it really just needs to let me create text faster/better than typing does, i'm not sure it needs to be voice based at all. maybe we "imagine" typing on a keyboard or move a fantom appendage or god knows what

It needs to be as accurate as the typing, though. Voice can do that. A BCI cannot capture a nuanced sentence.

I can't get voice accurate. For some people it might be but nothing understands my accent. It's very frustrating.

They're ~10 years or out so, based on current research.

Perpetually 10 years out you mean? BCI tech has not meaningfully changed in the last 10 years.