Blockstack is like a framework that allows people to create and access decentralized apps on top of it. It enables that by letting users created a decentralized ID that is stored on the blockchain (bitcoin) and giving users access to the apps based on that ID (like authentication).
Gaia is a storage system built by the Blockstack team. It is different from IPFS and others in the sense that it allows the user to choose where they store their data. This storage location is called Gaia hub. This approach gives users absolute control over their data which is unlike other distributed storage systems.
Even if Blockstack goes away, you can still access your data (in encrypted form) as Gaia is nothing but a storage system that is a wrapper over existing storage providers (aws, google cloud, and more). Now, the question is how you will decrypt it. Blockstack stores auth information on the Bitcoin blockchain so I guess you will be able to access your Blockstack credentials as long as Bitcoin blockchain is accessible and you have access to your secrets. Also, Blockstack and Gaia are open-source so it's unlikely they disappear with no trace.
Gaia is a storage system built by the Blockstack team. It is different from IPFS and others in the sense that it allows the user to choose where they store their data. This storage location is called Gaia hub. This approach gives users absolute control over their data which is unlike other distributed storage systems.
You can learn more about them here.
https://blockstack.org/what-is-blockstack/ https://github.com/blockstack/gaia