Yes. InDesign CS5 can open CS4 files. If what you want is the whole document, just keep working on it in CS5. But if you only wanted some of the text, then open another copy of the CS4 file and delete everything so as to have a fresh document with the same settings, into which you can now paste text copied from the first copy of the CS4 document. The fact that the new one has inherited the settings of the original CS4 file will make it so that all of the text characteristics will be retained.
Have fun!
Al