There is no reason to switch to a later Netscape, which would be outdated, if you have no use for the mail. firefox has the same format, i.e. bookmarks.html, as the later Netscapes (up to 7.2), and Mozilla (up to 1.7.12), or Seamonkey1.0. The current firefox is 1.0.7, or 1.5.0.1.
1.5.0.1 is parallel to Seamonkey1.0, while 1.0.7 is parallel to Mozilla1.7.12.
I think that you can import the bookmark.htm file from Tools|Import of your bookmarks, where the file content are placed into the existing file. Or, should you want something completely new, you could copy the bookmark.htm file, paste it into the new profile, and then rename it bookmarks.html, thus replacing the existing file.
Any reason why you want to switch to Netscape? I, personally, don't recommend the browser only 8.1, into which you could automatically convert the 4.8 bookmarks.
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.13) Gecko/20041220 K-Ninja/Samurai