I don't think they can add TLS termination because of the way it's implemented. NLB runs on Layer 4 - the transport layer where TCP/UDP run on. TLS technically runs on top of the transport layer.
That’s kind of the answer I was expecting, just hoping it wasn’t the case. From the marketing material they really want you to move, but not having a solution to offload tls makes it impossible for us. And it worries me to see the CLB getting effectively deprecated with it an alternative
I'm hopeful AWS will follow this up with ACM supporting SSL certs on instances, so you can run a LetsEncrypt equivalent on each instance, providing TLS end to end encryption