I definitely know for a fact he recorded his Avengers 4 cameo. It’s fitting that this is his last (or at least towards the end) as it’s the end of the greatest realization of his work
He did, although it wouldn’t surprise me if his Avengers 4 cameo will his final. Considering that the movie is going to be somewhat of a endpoint/reset for the current MCU and his age, I would bet that his cameo was written in the sense that it would be his last.
A titan has passed.
RIP Mr. Lee. Thank you for sharing your genius with us.

It’s hard to imagine comic books without Stan’s creative influence. He created so many beloved characters.
Thank you Stan for many of my childhood memories. I read a lot of your comics.
R.I.P.
Aw man. I thought he was gonna live forever!
He will, Biggirl, he will.
Rest In Peace, Stan.
There were fights in the family over the potential estate.
R.I.P. Stan Lee.
Well, yeah, he’s dead now, but they’ll retcon that soon enough. Nobody ever stays dead except Uncle Ben and Buck… Oh, right.
He wrote all the super heroes that were worth reading, at least for me.
RIP.
RIP, Stan the Man. You made my childhood and adolescence richer.
Damn good run to 95 and to see the material he worked on with others become dominant in entertainment. Glad to have been around to grow up with his work. On to the next adventure, then…
RIP, Stan the Man. You created the humanized super-hero, and as a result, humanity spread to super-heroes of others as well. (At least, until Grant Morrison took over writing them.)
Don’t be sad because it’s over, be glad that it happened.
Sad, but he had a damned good run.
RIP, Stan. You will be missed. 
It is hard to describe how much Stan Lee mattered to a kid growing up in the '60s. He mattered.
RIP Mr. Lee; you done good. Thank you.
When I was in 8th grade (like 1979 or so), I wrote a 4,000 word paper called “Modern Mythology” that drew parallels between ancient Greek & Roman myths and various Marvel comic heroes. Some of my earliest memories are of buying the 3packs of Marvel comic books in the early and mid ‘70s (these surely influenced my love of taking risks). Stan Lee has been a part of my life for all of my life, is what I’m sayin’. I’m sorry he’s gone but I’m glad he was here.
And, of course, there was Kirby’s own Funky Flashman. As you say, it was an obvious thing to caricature, but it’s always bothered me that some people seem to take that parody as a serious criticism of Lee.
Partly because Stan The Man’s public persona was so obviously the over-the-top hucksterism of a carnival barker, but also because he never stopped giving credit to everyone around him. Stan’s Soapbox was full of praise for all the creatives, and Marvel comics featured the now-standard credit box on the front page of each story, clearly crediting the writer, artist, inker and colourist, from 1961 — it would be years before DC gave similar credit to anyone except Bob Kane.
Thanks. Hadn’t heard about that - too bad.