As promised in this post, 2014 Roadmap and Migration Dates for Existing Developers here are the migration details regarding migrating from QuickBooks Online SDK to QuickBooks Online REST API v3.
All developers currently using the QuickBooks Online SDK (aka QBO XML SDK (SOAP)) to access QuickBooks Online company data.
Deadline for completion
09/23/2014 – Please read this post.
Benefit of completing the migration
Your app will be able to connect to QuickBooks Online “harmony” companies.
Impact of not completing the migration
Your app will not be able to connect to QuickBooks Online companies.
Customers will need to click the “Connect to QuickBooks” button inside your app, and authorize(via OAuth) your app’s access to their QuickBooks Online data. Please see the following documentation for implementation details: Implement OAuth in your App