TL;DR: I don’t see any practical path forward for decentralized stuff other than abandon the pretense of cross-chain value transfer and embrace balkanization, while letting the centralized stuff handle the cross-chain value transfer.
Fully private systems, like Aleo, will be mostly memoryless systems (memory will be provided only by an individual’s viewing keys).
These systems will allow for a class of application we haven’t seen online before - UTXO/records as rai stones that just happened to materialize along with a zkp.
Given that fully private systems will be memoryless black boxes with zero-knowledge proofs, one cannot verify that a contract path got executed in the exact same way that you would have wanted. Therefore, it makes no sense to cling to the notion of traditional execution, and one should focus on the result that one wanted to achieve.
This would seem to indicate that private systems lend themselves to intent-based approaches.