Toyota has kind of gone to that 10,000 mile oil change interval across the brand using TGMO 0w20.
2016 Avalons are now direct injected I believe and if you do a little research there's plenty of threads on here about how direct injection engines are tough on oil (something to consider with extended intervals). And one thing I'd worry about when going to a Toyota dealer...not all Toyota dealers are using TGMO 0w20...some are using cheaper stuff...so I'd worry about going 10,000 on say, some local no name distributer.
I'd probably go 7,500 on a quality synthetic for a while and see how that goes. And I'd check the dipstick periodically to make sure that you're always at the proper level. And I know the "color" of the oil means "nothing", but you are talking about a direct injection engine...carbon, fuel dilution, soot, etc, are going to be getting into that oil more than a regular injected engine. It probably wouldn't be bad to take a look at it around 6-7k thousand miles and go...wow! This stuff looks pretty bad.