We already know from the press release that at least 7 people will physically be in Rio:
Many of the former Olympians will also be there but not exclusively for Seven. There will also be at least a couple of reporters who travel over (Chris Reason and Alex Hart based on the promos but possibly others as well) so the team won’t be quite as skeletal as what you’re suggesting.
The only real difference this time around will be that the studio will be in Sydney or Melbourne rather than Rio. It’s a smart way of saving some money given that viewers will notice no change from past Olympics which have all been anchored from a dark, enclosed studio anyway.