Expecting Angular to support IE8 is highly unrealistic. Angular is innovative and different, IMO. To expect Angular to maintain support for IE8 is to expect Angular to sacrifice speed of development / innovation. Support of IE8 constrains the feature set that is possible in Angular. There's a reason Angular seems to be winning more independent/general developer mindshare than Ember, and this is the reason.
Anecdotally, I've noticed more established/larger tech companies (other than Google) using Ember, and more startups using Angular (with some exceptions like Amazon, which uses Angular). I think this is also a reason.
Dropping IE8 support + the "don't worry, it's free" Dart port make me very concerned about committing to Angular for anything I might be maintaining 2 to 5 years from now.