What made me jump boat on Construct 2 was the hard time I had by lack of support on both Spriter and Spine's third party plugin. It would be amazing to have those being an official solution for us.
As of r109, we believe there are now enough features available in the Custom Importer API for tools like Spriter to be able to write and maintain their own importers as third-party addons. This is available to any tool such as Spriter, Spine, Dragon Bones, and any others. It removes the need for the developers to get us to implement formats they've designed themselves. Since we've done our part and it's now up to third-party developers to use the available APIs to create importers, we're marking this feature as 'shipped'.