What terrifies me is not the potential data leak, but that the NSA may be obtaining their TLS certificates, bypassing the threat (to them) of "https everywhere".
You mean private keys. Reddit uses forward secure TLS, so obtaining the private keys does not allow the NSA to decrypt the traffic, as fresh keys are negotiated on each connection. The long term private key is used only for identification, so they allow you to impersonate the server but as far as I'm aware, nobody has yet seen evidence of a large, popular website having all of its traffic hijacked by state actors with stolen SSL keys. I can only imagine that such an attack would be quite visible (unless the taps were done internally inside a big CDN).
Also, the SSL keys are not stolen, we have to assume that they have been given to them based on the letter. The gag order and canary indicated that everything has been compromised.
If it's not a direct real-time feed then, no, doesn't really change much.