Diffie Hellman doesn’t ever send the key over the wire, that’s the point. There is nothing to decrypt in the packets that tells you the key both sides derived.

Unless they break ECDHE, it doesn’t matter if RSA gets popped.

Diffie Hellman to the best of my understanding also relies on the same hard problems that make the public key cryptography possible. If you trivialize factoring of big numbers, you break both RSA and the original DHE. Not sure how it will work for elliptic curves, but my instinct tells me that if you make the fundamental ECC problem easy, the exchange will also go down.

wouldn't be surprised if ecdhe isn't quantum resistant.

Something tells me that by the end of the century only the one-time pads will still be holding their secrets.

Even for that to work you need a good random number generator

That's pretty trivial. xor a video camera with AES and no one is decrypting that ever.

And, famously, the camera is pointing at a lava lamp, ha ha.

Honestly not sure how they created one-time pads 100 years ago.

In one case it was people just banging on typewriters randomly.