But remember in season 2 Bailey had been married for 10 years to Tucker so maybe she didn't start out as a surgeon right away. She does look older than most other 5th year residents (Callie???) so maybe she just had a later start in the medical field!
I personally think that Christina and Owen are going to be the ones getting married! All of the spoilers have been hinting at a big surprise wedding and well Meredith and Derek getting married wouldn't be a huge shock and Alex and Izzie wouldn't be a huge surprise either given the circumstances that they are in right now! So my guess would be a wedding!!