This is just my opinion/perspective, as a developer using Angular for over 2 years, and from general open source developer perspective.
Open source release timelines are never guaranteed. The Angular team and community will take as long as it takes to build it the right way, and I prefer that over fixing a date and rushing to meet it. The road from 0.9 to 1.0 was almost two years, because of real world usage of the framework gave very important feedback that became incorporated into Angular. The plans for Angular 2 are ambitious, and in many ways will have to go through a similar process of trial by fire to establish best practices and framework design. Its going to take time to nail down the right APIs even if they have the foundations planned now, and since Angular 2 is full of a lot of major changes, its not just a matter of making a few changes to the current 1.x branches. I doubt many of us can delay our business decisions based on the estimated and not guaranteed estimates of a new framework release, not even including the time it takes to learn the new version.
As a developer I urge you not to let the future impair your ability to develop and release something in the present.
Indications are that Angular 2.0 is not going to be an upgrade to implement, it will be a migration or major refactoring. With that in mind, The 1.x branch will likely remain in force for some time and not require immediate changes to existing applications. Any code is subject to laws of maintenance, and Ionic will also require some changes. As I’m digging into the depths of Ionic’s source code, you can know that its pretty well structured and organized. Many aspects are abstracted outside of Angular, so I don’t think we will need a full rewrite. The real challenge is likely to be how to best build with Angular 2, and then mold Ionic to fit into that paradigm.