Newer versions of InDesign should be able to open your CS2 files, but if you still have a copy of CS2 running I would strongly recommend tyou export them to .inx and use those for conversion instead. There are occasional issues with file corruption when opeing legacy files in CS5 and later. You also should expect the text to reflow due to differences inthe text engines between versions (but this will not happen with a converted .indd fileuntil you begin to edit a story), so pay close attention to page endings and overset text.
If you cannot export .inx from CS2, the next best thing would be to open the .indd files in the new version, the immediately export to .idml, open that and save with a new name to protect th original files and clear as much potential corruption as possible.
Newr versions can normally open older documents. But depending how the typesetting is done the document might change, text could reflow. Adobe has improved its type engine for better results. If you open the document the first time it should stay as it was created, but in the very same moment you make the lightest change to the text it will reflow according to thenewer text engine's rules. If the typesetting was corret, it should not be a problem, because the newer engine is better than the old one. But if some manual adjustments have been done it could cause problems.
You have to check your document anyway.
If you save the document as inx from CS2 and open it in a newer version, text will reflow anyway according to the newer rules.
If you need the very same document for fuure use, export this document as PDF with no downsampling of resolution, embedded fonts, no transparency flattening, not color conversion and its bleed from CS2. You can place that document in future InDesign versions without any changes.