These NLP systems are tailor-made for this type of use case, and Facebook is undoubtedly already experimenting with a Google style ‘contextual ad-words’ type of model where ‘packets of knowledge’ and keywords can be bought, and then a transactional service (like your Uber example) is then provided as the call to action.
I suppose one of the downsides is the potential for this form of contextual advertising to become too intrusive. Imagine if your conversation was of a more personal nature, like you’d just found out you were having your first child. I remember back in 2011 a few of the big tech co’s in SV warned their staff not to use Siri for anything work related (like setting reminders or creating meetings) for fear of this being analysed.
The ‘next step’ you describe is already there for many use cases, but most of the NLP systems (Siri, Alexa, Google included) need more language handling skills to be really effective (like contextual memory, topic switching etc)
It’s an exciting future though, especially when you add other inputs from IoT and gesture control into the mix.