Teams and players wont go all out during the preseason at any professional sport. Sometimes the starters may only play a few minutes (or a drive or 2 in the nfl)If Lebron were to get injured playing an exhibition and couldn't play in the Olympics it'd hurt the team more.
No one is going to beat this team. (And yes, I think this team would compete with the dream team) All the simulations i've seen of the odds if the 2012 team were to play the dream team only gave a slight edge to the dream team. (Dream Team would win about 53% of the time)
Obviously simulations cant be taken at total face value, but we'll never have the ability to see 92 vs 2012 so this is as good as it gets.
I do however think this may be a weaker team than in the past... if we lose the Gold Medal it will be because of Rudy Fernandez, Ibaka, and the Gasols (Ricky Rubio is injured).... France might be a surprise contender... But i'd say the US is still more likely than not to win Gold.