Would it be possible to have some kind of API Schema version, so that it would be easy to query if changes on schema happened, therefore changes in plugins need to be implemented? Usually it is done by maintaining compatibility for couple months allowing 3rd party applications to cache up and then deprecating old things.
I do have need for PayPal and e-commerce integration and in long term it would be nice to have banking integration and maybe expenses submit from mobile apps, other users probably have other needs.
Do you have any vision how you want extensions and integrations to work?