ALL-NIGHT SPORTS fans, news junkies, movie buffs and public-service advocates who live in the District have at least another year to rest up for the arrival of cable television -- but at last the deal is being sealed. Almost every conceivable political, legal and money-mooching challenge to the franchise-awarding procedures has now run its course. Barring some hideous legal or financial surprise, District Cablevision Inc. is commissioned to wire the city and provide the service. How well it sells will be up to the viewers, but that's another story.

Here is the cable television outlook now that lawyers have settled the last lawsuit: District Cablevision will have a 15-year franchise. It has chosen the Chesapeake & Potomac Telephone Co. to do the wiring, an arrangement that has been approved by the Federal Communications Commission and that has been deemed workable by the Justice Department in the light of the final court order that broke up the Bell System. District Cablevision has one year to secure financing for construction of the system, and it must begin building the 1,155-mile wiring network within 18 months. Construction and service must be ready for at least 14 percent of the houses and apartments in each of the city's eight wards by April 1986. By April 1987, service must be provided to at least 43 percent of the homes in each ward.

Nothing in all these stipulations requires that any percentage of the residents in these wards actually subscribe or watch the programs, of course. But there is comfort in the fact that the District seems to be avoiding many of the costly mistakes made by cities that negotiated cable franchises that insisted on unrealistic equipment, service and costs. City officials here as well as District Cablevision's investors have been keenly aware of those failures elsewhere and undertook detailed reviews before the franchise was awarded. Having gone through those channels, they can now turn to the ones to come on the viewers' sets.