I think this is indeed a very, very brave move for Ricciardo, and frankly it left me gobsmacked when it announced earlier.
If I was a betting man I'd have expected him to stay at RD, even with Honda, on maybe a 1 year contract as he keeps his options open for either a). a better seat at Merc / Ferrari in future, or b). to see if Honda manage to pull up their socks and build a winning engine.
For me to stay at Red Bull still has advantages for RIC, as even if next year they fall down the order somewhat, racing against, and beating Verstappen keeps him in the limelight and looking impressive.
The problem with Renault, assuming they remain where they are in the competitive stakes, is having a good session / race against Hulkenberg doesn't have the same level of prestige as it does against Verstappen, and I worry that if Renault don't produce a winning car, Ricciardo could well start dropping off the radar of teams / fans as a potential WDC.
To be clear btw, I think Ricciardo is one of the top 3 or 4 best drivers in F1, and I also rate Hulkenberg very, very highly.
We've seen this all before sadly. Thinking of (but not to the same level of talent admittedly) people like Alesi when he left Tyrell, Hulkenberg, Alonso etc.. the list goes on!
Anyway, all said and done, I hope and pray it works out well for the bloke, as a competitive Daniel Ricciardo is a very good thing for the sport.