CBS says it will be number one. NBC says too much attention is paid to being number one. ABC says it IS number one, so who cares what numbers two and three say? These networks are such children.

And the opening of a new network season for all the scientific testing and conference-room calculation that has gone into it, is to some extent a sweep-stakes and to some extent a duck-shooting game on the midway. Which ducks shall survive the first few months - or weeks? There is only one unanimously certified sure-thing, ABC's lavish "Stars Wars" superclone, "Battlestar Galactica."

MOST LIKELY TO SUCCEED

"Taxi" (ABC).

"Vegas" (ABC).

"WKRP in Cincinnati" (CBS).

"In the Beginning" (CBS).

PROBABLY OR CERTAIN TO FLOP

"Apple Pie" (ABC).

"The Paper Chase" (CBS).

"Flying High" (CBS).

"American Girls" (CBS).

"Lifeline" (NBC).

"W.E.B." (NBC).

"The Waverly Wonders" (NBC).

"Who's Watching the Kids" (NBC).

"Sword of Justice" (NBC).

"Dick Clark's Live Wednesday" (NBC).

Everything else is in the who-knows? margin.

Shows like Mary Tyler Moore's new Sunday night hour on CBS will have rough going because of hefty competion, and even standbys like "Rhoda" and "All in the Family" face trouble.

"Rhoda" goes into its fifth season with only a 13-week commitment from CBS - Almost unprecedented for a long-running show. And "All in the Family" will no longer have Mike and Gloria as foils for Archie Bunker. In addition, the show is being taped without an audience, over two days instead of one - at the insistence of star Caroll O'Connor - thus increasing production costs.

It could also be true that "Happy Days" and "Laverne and Shirley" have their most succesful hours behind them; there is just so much more that can be done with The Fonz, and Paramount's wardrobe department must be running out of chicken suits for Verne and Shirl."Welcome Back, Kotter" will be honored with the presence of lumpen hearthrob John Travolta on only a third of its episodes this season, so it could be doomed. So much the better; the show never was any good, anyway.

Other returning shows will undergo heavy tinkering to help insure longevity. Farrah Fawcett-Majors herself will return for six episodes of "Charlie's Angels," including the first one. Young Quinn Cummings, of "The Goodbye Girl," has joined the cast of "Family" to enhance the cuteness quotient.

A pretty woman cop will be added to the team on NBC's "CHiPs." Virtually the entire cast and crew of "Operation Petticoat" have been scuttled, though a show by that name, about horny men on a sub, will return. The Ingalls family, daughter Mary now blind, have moved to a big city from their "Little House on the Prairie"; two little-boy twins have been added ot the cast. Oh joy.

For some of these shows, time is running out. Jack Webb's laborious "Propject U.F.O." can hardly be expected to last another season, especially once views see the superior hardware of "Galactica."

We make such prediction on the basis of industry scuttlebutt, a program's placement in the schedule, and hours of arduous pre-screening of new series at network offices in Hollywood.

The predictions aren't exactly fool-proof; last year it was declared here that "The Betty White Show" would be a smash and that "The Love Boat" would be "one of theose mediocre successes that hangs around but never really matters." Well, it never really will matter, but its success was hardlyiffy.

We were on the button, however, in foreseeing early deaths for "Young Dan'l Boone," "Big Hawaii," "The Oregon Trail" and "We've Got Each Other." Indeed, it is hard to remember now that such programs were even on the air. Television entertainment has always been of the disposbale and transitory sort, but the Kleenex factor in TV series production seems to grow more dominant each year.

Sooner or later, some unidentified flying object is going to have to interrupt this annual lemmings" sack race to the edge of night, and perhaps a better system will result.

Of course, there is no evidence to support such a hope.