Okay, let's approach this rationally and logically, rather than as Adam fans. Hypothesis: Adam will perform with Queen at the closing ceremony of the Olympics.
Proof:
1. Queen will perform for the closing ceremonies of the Olympics this summer.
2. Queen will perform with Adam Lambert for 6 concerts this summer.
3. Queen and Adam will put in a great deal of time rehearsing and working on a spectacular show, which will be perfected after the 6 concerts.
4. Therefore, in terms of time and effort, it is only logical to use the same frontman for the Olympics, rather than spend more time and effort for just this one-off.
5. The Olympic performance will be massive. Seen around the globe. It is only logical to use a frontman who can perform Queen songs with world class, huge vocals, and who, simultaneously, has a massive stage presence necessary for such a world stage. It is widely acknowledged that there is no other singer in rock/pop today who can sing with the range, power, and finesse of Adam Lambert. He also has a reputation for eating the stage with his presence.
6. Therefore, Adam is the obvious - and only - candidate to appear with Queen at the Olympics.
7. Therefore, it is only logical and rational to SQUEEEEEEEEEEE and jump for joy that Adam WILL perform with Queen at the Olympics.
QED
