Figuring out how our current resource allocation might be shortsighted, what trends are we missing out on might be a good topic for the summit. My bet for that would be artificial intelligence (in the wide sense, including natural language processing, machine learning etc). User interfaces are getting more and more clever: they understand what you want without requiring you to become an expert in their syntax; they can guess what you will want next; they can relieve you from repetitive tasks by learning how to do it and let you focus on tasks with more added value. Your phone understands what you ask from it; the search engine you use tailors its answers to your past interests; soon your car will drive itself.
When the shift to mobile happened, Wikimedia was late to recognize its importance; out mobile interface was significantly delayed compared to other top sites, and had to be monkey-patched on top of a system that was not built with such a use case in mind. There is a danger that we repeat that history with AI. There are various initiatives that already involve or might benefit from AI tools (NLP in Discovery, article feeds based on past visits in the apps; suggestions in the editor; ORES; and chapter and third party initiatives like Wikispeech), but they are disconnected and not really part of any organization-level strategy, and in some cases suffers from inequality of investment and benefit (where everyone is happy to use an API but no one helps with its development - it seems ridiculous, for example, that the Foundation does not employ a single developer to work on ORES, which is really the only plan we have for addressing editor decline).
I might be misjudging the trends (AI is well outside my area of expertise) but my impression is that this area is way too important to happen in an ad hoc, skunkworks way; there should be a unified strategy, more support from the users to the providers of the machine learning infrastructure, and exchange of knowledge between Wikimedia developers working in a similar are, and between Wikimedia developers and external experts. WikiDev17 might be a good place to work towards that.