My guess is it will be just like the web site describes. They will likely have an open event there at the event center, which will mostly have people who are either already vaccinated or willing to risk attendance, will have mask and distancing requirements, and the event will also have significant online presence. International in-person participants will be more limited due to travel restrictions, but virtual attendance will be huge, potentially multiple times regular attendance numbers.
Since many people have successfully run virtual conferences (I've attended several) the common difficulties are easily understood.
Presentations can be pre-recorded or live, both are straightforward. A mixed venue can have some presentations that take place with in-person viewing on a large display for remote/recorded speakers, and a lectern and camera for live speakers. Social rooms and other mingling is also straightforward, and often less intimidating than physical spaces, and with some cameras and group chat can be easily handled. In-person rooms can have a small conference room while people online can be individuals in video chat. Demos floor breakout rooms become chats run by individual vendors showcasing whatever they want, which they can do from the safety of their own homes showing on live video, or in person with cameras on a demo room floor.