10-20 years from now? Maybe. It depends on whether or not the industry will cut corners in this part of the experience. I find it hard to predict which features get polished, and which are forever left barely-functioning. Might depend on which are on "critical path" to selling subscriptions.
0-10 years from now? We'll still need the options page.
"Email signature" options page provides visibility, consistency, and predictability. That is, you can see what your e-mail signatures are, you are certain those are the ones that will be used for your message, under conditions defined in the UI pane, and if you change something, you know exactly how it will affect your future e-mails.
LLMs are quite good at handling input, though not yet reliable enough. However, as GUI replacement, they are ill-suited for providing output - they would be describing what the result is, whereas the GUI of today display the result directly. As the writers' adage goes, "show, don't tell".
(That said, the adage is way overused in actual storytelling.)
Think less "make a signature for me" and more "here's the signature I want to use, make it my default."
Then the model would map to either Outlook / Options / Signature / fields or directly to whateverSetSignature().
From that more modest routing requirement, it seems a slam dunk for even current models (retrained to generate options paths / function calls rather than English text).
LLMs could certainly help loosen the input requirements, not to mention aim some sorely needed hype back in this direction. I am afraid that they will murder the latency and compute requirements, but hey, progress is always two steps forward one step back.
For a while, ubuntu had a local search where you could hit a button (super?) start typing, and it would drill through menus at lightning speed
Originally: Taxonomically organized nested menus, culminating at a specific function or option screen
Now: Usage-optimized Ribbon (aka Huffman coding for the set off all options), culminating at a specific function or option screen
Future: LLM powered semantic search across all options and actions, generating the exact change you want to implement
Why have an "email signature" options page at all, when an LLM can stitch together the calls required to change it, invoked directly from English text?