This question suddenly came to my mind so I decided to ask you, Ext developers, about it in an informal way. This is curious because the things that latest browsers natively support allow one to code less workarounds and polyfills etc. (which are not always affordable) and relying on robust native API focus on actually developing the application. But the need to support old browsers (of course not exclusively IE but mostly ) result in a huge ballast of fallback code in your base increasing library size and likely somewhat decreasing overall performance even in modern browsers because of numerous checks.
So what do you think, are there any heavy fragments you are dreaming to get rid of once you stop supporting browsers like IE6-IE8?