Yes, InDesign can open any older version's files.
I would hurry up and buy the latest version CS6, while it is still available. The "Creative Cloud" version, launched in June must be RENTED on an annual basis, charged every month. If you stop renting, you haven't got an app to open your files with. Given that you haven't upgraded in several years, buying CS6 will represent much better value to you.
You'll find lots of very useful enhancements and features since ID 2.0.