Many, though not all, of your AppleWorks documents will open if you purchase iWork, but iWork can't handle AppleWorks database or drawing files- only word processing, spreadsheet, and presentation files and not if those files were created by older versions of AppleWorks or its predecessor, ClarisWorks.
MSOffice can sometimes open AppleWorks files but the results can be very messy.
Alternatively you could create a separate partition on your hard drive, install Snow Leopard on it along with AppleWorks, and boot into SnowLeopard any time you need to use AppleWorks (which is the way I've done i).
But in the long run you'll have to abandon the old AppleWorks files. I have thousands, some of them going back to Claris Works, and I'm slowly converting them all, one by one, into a different format that Mountain Lion can read.
But my old AppleWorks databases (worth $$$ thousands in terms of the information, business contacts and data etc. in them) are gone, unless I open them in Snow Leopard.
For the future, it would be safe to assume that anything Apple gives, Apple will probably take away later on - so I wouldn't rely on any particular application always being available, or operable, until the end of time.