So Silverlight, Flash and Flex are dead. Or maybe not. Honestly we’ll probably see all three around for years. Enterprises love to hold onto outdated or deprecated software (er IE6) so they’ll probably continue using these three until the development tools are dead. Given how many VB6 and VBA apps I still see out there, it will probably be years before they are gone from our browsers.
The big question of course is what will Esri do with those APIs? Well don’t fear, they are totally committed to you writing apps in libraries that have no future.
Seriously, if I was Esri… I’d totally get Leaflet working natively with Esri APIs out of the box and use that. Lightweight and fun. Something Esri’s heavy APIs lack.