It's beginning to look like the Writers' Guild of America is headed down the same path as the one taken by PATCO, the air traffic controllers' union that struck itself right out of business during the early years of the Reagan Administration.

Last week the writers resoundingly turned down what was called "the absolute final offer" by the Alliance of Motion Picture and Television Producers. In doing so, they turned a deaf ear to a group of dissident guild members headed by powerful producer-writers Steven Bochco and Stephen J. Cannell, who claimed the offer was "decent" and "a vast improvement over what we had and certainly more than we expected to get." The group urged writers to accept the offer or risk disastrous impact on the entire film industry.By a 3-1 margin, the writers say they are willing to take that risk. Seems that even though producers sweetened the financial pot, they didn't suit the guild with regards to overseas sales and residual payments for hour-long programs.

So the writers have decided to stand firm, and negotiations have broken down completely. "We've finished talking," said Alliance spokesman Herb Steinberg. "We won't go back."

"This vote is awful for the industry as a whole, but especially for television," said Bob Gersh, a show business executive. "The networks face the possibility of losing all their first-run television programming for the fall season. The new season could now be moved all the way back to January, or lost altogether."

Neither option is particularly appealing to the networks, who are already losing viewers to cable, independent and public television and video cassettes at an alarming rate. So with the bargaining table indefinitely turned upside down, TV producers are scrambling to find non-union scriptwriters or guild members who are willing to cross picket lines.

Guild representatives doubt that approach will be successful. "They were claiming they would attempt to produce with scab writers," said Guild spokeswoman Cheryl Roden. "We don't think that will be any significant help to them. No one is crossing the lines."

But some writers, discouraged with the long lay-off, are beginning to weaken. "The union isn't listening to us anymore," said former "Hill Street Blues" writer David Milsh. "They aren't thinking about the guy who needs to work and put food on the table. All they're committed to now is strengthening the union."

And that may not be enough for union members - especially not with the jobs of 200,000 people employed in industry-related fields endangered and studios and networks talking about major layoffs.

Which is why some industry observers expect to see the Writers' Guild eventually crumble. Big-name producers like Bochco and Cannell won't be able to afford to stay on strike much longer, and they will bolt the union or sign independent contracts, taking more and more maverick writers with them. Increased dissatisfaction among the union rank and file will weaken the Guild's bargaining position, resulting in either a weak-kneed agreement or a PATCO-like resolution to the industry's 18-week nightmare.

* WITH THE STRIKE continuing, Late Night With David Letterman is trying to return to television - sans writers.

The show will begin its comeback attempt tonight even though "Late Night" producers have been unable to secure a waiver from the Writers' Guild that would enable the show's writing staff to return to work. Similar waivers have been granted to "The Tonight Show" and "The Cosby Show," but so far the Guild hasn't seen fit to grant one to "Late Night."

So Letterman will be on the air tonight, but he'll pretty much be winging it. He can't even write his own stuff, because he is also a member of the Writers' Guild. But he can return as a performer, which means he'll be able to offer a few "casual remarks" at the start of the show and then get right into interviewing guests such as L.A. Laker coach Pat Riley and rocker Graham Parker (tonight), Dudley Moore (Wednesday) and Sandra Bernhard (Friday).

The interesting thing is, "Late Night" has always had the look and feel of an improvised program. Now we'll have a chance to see how much of that improvisation is scripted.