My two cents having had the news settle in and marinate in my mind:
I'm cautiously optimistic. This is not how i wanted the greatest Marvel villain of all to make his MCU debut and no way you slice it, this was Feige and the Russos trying to come up with a gimmick to subvert all our expectations and get tongues wagging. And its working. This news broke the internet and is in my opinion the biggest, craziest cbm news we've gotten ever since Ben Affleck was cast as Batman and was announced to be going up against Henry Cavill's Superman. For the next three years, Marvel will be dominating the news cycle just like DC was circa 2013-2016.
Now.
I don't think Feige is stupid. I think he knows whats at stake here and I HAVE to think that even though this was done partly out of desperation, that there isnt a method to the madness. RDJ is one of the richest actors in Hollywood. The man has enough money to retire on an island somewhere and not work a day more in his life. I dont think RDJ did this for the money. I think he's doing this to prove that he can flex an acting muscle that he's not yet used. I think RDJ is going to go full dark and intense in this role and surprise us all with his performance. But as you guys have said, just by virtue of it being HIM, we will never not be thinking about Tony Stark.
I think Downey has a chip on his shoulder and he's out to prove to everyone, and himself, that HE can be both the greatest Avenger in the MCU and its greatest villain. I mean that tagline pretty much writes itself doesn't it?