Another downside of the season, and you touched on this briefly, is IoT devices. Sales will only increase in future years as more and more devices become internet connected. Fridges, cameras, baby monitors, thermostats, light bulbs, the list goes on. These things flood online in droves the day after Christmas/Cyber Monday as these items are often on heavy discount.
With the Mirai IoT botnet software open sourced and still a threat we haven't fully mitigated, the holiday seasons can bring even more vulnerable IoT devices online, giving attackers more targets and more bandwidth.
Yes, IoT security is a huge trend. I have a few post that talk to it, but it will be a big topic I will be covering in the future as well.