Blobs are part of the chain just like calldata is.

Today (or rather, this week), default nodes store blobs temporarily, but with EIP 4444 calldata is going to get the same treatment.

The endgame has for a long time been: all nodes do real-time validation; p2p networks store history.

How will we guarantee that history remains available once full modes forget it by default? Is there a p2p network that can provide a strong guarantee?

the portal network is supposed to do this

https://ethresear.ch/t/using-the-graph-to-preserve-historical-data-and-enable-eip-4444/17318