Since the module interface has not changed basically, you will be able to replace it.
CKEditor of V1.6 is V3. Many plugins of CKEditor are shifting to V4. I think if you there is no plan to use new feature, replacement is a good idea. However, as with the new version has some issues, old version have also some issues. In particular, you will need to pay attention to security issues. If you would like to use CKEditor V4 and respect compatibility with Q2A V1.6, there will be a method to use my CKEditor4 plugin.
- Q2A V1.6.x: 3.6.6
- Q2A V1.7: 4.4.6
- Ckeditor4 plugin: 4.4.5