Would the Secure Enclaves such as Keystone or Intel SGX obviate the need for cryptography Would the use of Secure Enclaves such as Keystone or Intel SGX obviate the need for cryptography? Rendering cryptography irrelevant in the decades ahead?
No, Secure Enclaves do not obviate the need for cryptography.

For a start, Secure Enclaves typically receive their input data integrity-protected or/and encrypted, which requires cryptography both within the enclave, and outside (perhaps in another enclave).

Even if we turn the question to "Would the use of Secure Enclaves obviate the need for unrelated cryptography", the answer is still no. Secure Enclaves aim at creating a virtual secure computer not under control of the person holding the enclave, and that does not match all use cases. Even in an Orwellian world where Secure Enclaves are the only form of secure data processing permitted, I bet both a master of that society, and any rebel, will want to use raw cryptography. And I see no practical way to prevent that, as long as programming remains a thing. We can do AES-256 or RSA-4096 in any computer language, including a spreadsheet.