No, there won't be one unified format. But it is highly unlikely that any new formats that are on the same level as DVD will be developed either.
If you want support for all of these, just get an LG 4160 or 4163 drive. It supports everything and has very good burn quality as well. Though DVD-RAM is very unpopular outside of Japan, so it's still pretty safe to get a drive that does not support it.
Also keep in mind that R, Rw, ROM and RAM all serve different purposes. It would be silly to merge these all into one format.
In 2005-06 the new generation of storage wars will start, and we will all get confused by Blu-Ray vs. HDDVD. This will be the next format war. (Companies are so stupid that they would rather confuse the customer and reduce their sales with multiple competing formats, than just have one single lone format that everybody supports.) These next gen technologies are not comparable with the current DVD technologies, and will require different hardware.
You can wait for years and years, there will always be something new over the horizon. Current DVD writers are quite inexpensive right now, and IMO it's the right time to buy.