Looks like a decision was made via @tomdale at: https://github.com/emberjs/rfcs/pull/45#issuecomment-93009469
This has been an amazing discussion. Big thanks to everyone for contributing your perspectives.
After reviewing this thread, it seems clear that the vast majority of Ember users who have responded, including people working at large corporations, are comfortable with dropping IE8 support in Ember 2.0. On the other hand, while there is enormous support for dropping IE9 support as well, a number of people still rely on support for IE9, and the benefits of dropping IE9 in Ember 2.0 are not as strong.
After reviewing this thread, many in-person conversations with Ember users in large companies, and reviewing the private data sent to us via email, we have decided that Ember 2.0 will support IE9+.
So how are we going to manage this transition, and what should you do if your business still requires IE8 support for the time being?
1.13 with Extended Browser Support
The core team will continue to periodically release point releases in the 1.13 series to patch security bugs and browser compatibility issues, including issues in IE8.
No new features will be added, and we should be clear that we do not intend people to stay on this release unless they must support IE8. Our Semantic Version guarantees mean that the vast majority of the community should migrate to the 2.x series as soon as possible.
It is important to note that Ember 1.13 will come with deprecation warnings for everything that we will break in Ember 2.0. As a result, if you are running Ember 1.13 without any deprecation warnings, you should be able to easily upgrade to Ember 2.0. And because of the Semantic Versioning guarantees in the Ember 2.x series, it should be relatively simple to upgrade from Ember 1.13 to the most recent version of Ember 2.x when you are able to drop IE8 support.
For example, imagine you build the Ember app for Big Widget Enterprise Co. that requires IE8 support. You upgrade to 1.13 (the last release in the 1.x series) and, over time, refactor code to eliminate all deprecation warnings. Periodically, you apply 1.13 patch releases to maintain browser compatibility and to fix potential security issues.
Then, in April of 2016, management decides that enough customers have moved off IE8 that you no longer need to support it. At that time, Ember 2.6 will be the most recent stable release. Because 1.13 without deprecation warnings is forwards-compatible with Ember 2.6, you can upgrade from 1.13 to 2.6 with little hassle.
With the integration of Ember CLI and Ember Data into the Semantic Versioning guarantees, many of your dependencies will follow a similar upgrade path.
Of course, the above guarantees only apply to Ember, Ember Data, Ember CLI, and the rest of the core-supported packages. Addon authors are free to define their own support matrices. We encourage those who depend on older browsers to contribute back by submitting PRs to the addons they use with compatibility patches. Likewise, we encourage authors of existing addons to work with users to offer a browser compatibility matrix as close to the core projects as possible.
If you require support for IE8 (and as a result, Ember 1.13), make sure to make your voice heard across the addon ecosystem.
That said, you should expect that new addons that come out after Ember 2.0 will not target Ember 1.13, and you should factor that into your decision to remain on the 1.13 Extended Browser Support release of Ember.
FastBoot, our effort to bring server-side rendering to all Ember apps, is designed to offer even users with slow, low-feature browsers a fast experience. While most people think of this as a benefit to mobile users, IE8 certainly qualifies as a slow, low-feature browser.
In our RFC, we mentioned that dropping IE8 will give us the opportunity to remove jQuery as a strict dependency. We should have been clearer that we have no intent to remove the Ember APIs that delegate to jQuery (such a Ember.$ and this.$() inside components).
Because these APIs will remain in 2.0, both for ease of upgrade and because we have not yet made the jQuery dependency optional, Semantic Versioning prohibits us from removing them until at least Ember 3.0.
On a personal note, we rely on jQuery heavily in our own apps. We think it’s a great library that remains hugely valuable to smooth over clunky DOM APIs and browser quirks (even in modern browsers). For those users who need the absolute smallest payload size, we don’t want to saddle you with a dependency that you don’t need. But we expect the majority of users to continue using jQuery, and we have no plans to remove the Ember/jQuery integration at this time.
Thank you again for everyone who took the time to help us make this decision, and thank you so much for being a part of the Ember community.