The Wonder had a dry dock in 2006. If they dock every three years then she's due in 2009. I took a quick look at the schedule and it looks like she might be scheduled for early October (her last cruise looks like a 3-night on Sep 24th and the first date in Oct is the 18th).
Not sure what she would be getting done other than refurbishment. There might be some additional things depending on what is done on the Magic this year, but I'm guessing nothing special since the new ships will be coming out in a couple of years.