Personally, I think 32 bits is enough for any application I'd care to run. If you need more than a few GB of memory, IMO the application is being ridiculously wasteful. But YMMV -- if some people think it's fun to debug 16-digit hexadecimal numbers, I'll quote Mr. Knightly: "I have nothing to say against it, but that they shall not choose pleasures for me."
IMO 64 bits is for mainframe operating systems. For my personal use, I prefer something... well, more personal.
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.