In the sugarplum dreams of the multimedia industry, there's a CD-ROM glittering under every Christmas tree this year. But chances are that at least a few disc publishers will find their stockings filled with ashes and soot. Because CD-ROMs sold in surprising numbers during the 1993 holidays, 1994 saw a piranha tank of activity aimed at this holiday season. Book companies set up multimedia divisions and announced product like Macbeth: The Game (due in 1995 from Simon & Schuster). Hollywood studios set up multimedia divisions and announced product like Blown Away (just out from IVI Publishing). The ensuing CD-ROM glut is sure to confuse consumers, and may even result in an early industry shakeout if lower-than-projected figures come in next year.,p> As a result of this overcrowding, good new titles have more and more trouble finding their audience. The retail landscape is also changing-CD-ROMs you once found only in computer stores are increasingly available at Barnes & Noble, Wal-Mart, and Blockbuster but it's still an immature marketplace. Moreover, there's usually no way a potential buyer can preview the product in the store. ''There's no established rental chain,'' says Doug Millison, editor in chief of Morph's Outpost on the Digital Frontier, a magazine for multimedia developers. ''Being able to rent a video game at Blockbuster is an amazing mechanism for helping to sell that same video-game cartridge.'' Add to that the technical difficulties in getting many CD-ROMs up and running, and the horizon looks foggy. At the same time, some who observe the industry remain upbeat. Kevin Kelly, executive editor at the hip technojournal Wired, is convinced that the CD-ROM won't truly take off for another two to three years, but he's not writing off this season's make-a-buck titles. Why? ''I don't think you should underestimate the public's appetite for junk.''