A crane looms over the construction site of the future Restion Station parking garage, which is framed by Reston Town Center and the Dulles Toll Road. Metro's new Silver Line, which will serve the Reston station is expected to open in about a year. (Jahi Chikwendiu/THE WASHINGTON POST)

Near the shell of the new Metro station in the median of the Dulles Toll Road in Reston, cranes tower over a yawning construction pit where a $750 million complex — including an underground parking garage, apartments, offices and a hotel — will rise.

Columns have been erected for the pedestrian bridges connecting the Wiehle-Reston East station to the town of Reston on either side of the toll road. Nearby is a mini-storage facility whose owner has already asked the county for permission to rezone and redevelop the property into more homes and office space.

The first leg of Metrorail’s Silver Line, which would run from East Falls Church to the eastern edge of Reston, is more than a year away from opening, and already there are signs that it will spawn some of the development that advocates promised it would. But it is also clear that it may take years for some of that long-awaited growth to actually happen.

For all the anticipation of the station’s scheduled opening in December 2013, there are also concerns about the future of the next phase of the Silver Line, which would extend the line to Dulles International Airport. And some developers are biding their time while county planners work on the guidelines that will dictate what kind of development goes where.

“I would say there is a lot of interest and a lot of jockeying for position as to where the future is going to lead them,” said Mark C. Looney, a land-use lawyer who used to work for the county. “For the last decade plus, all this rail has been lines on a map, or circles on a map. You could theoretically understand it, but it wasn’t real life. Now you can understand it. But there’s not a lot of shovels in the ground.”

After more than two years of planning, a task force of county staff members, residents and property owners is still working on guidelines that would dictate the redevelopment around the new station, including an urban grid, parks and more residential and commercial development.

Meanwhile, others are anxiously awaiting a decision from Loudoun County’s Board of Supervisors on whether to opt out of the Silver Line’s second phase of construction. Several board members have expressed concern about the cost to the county and a union labor incentive the agency managing the project gave contractors. The county has until July 4 to decide.

Other stakeholders worry that a decision by Loudoun to walk away from the $2.7 billion project could delay and even jeopardize its completion. At the very least, it could create more congestion in Reston and especially around Wiehle Avenue, which was not intended to be the terminus for Northern Virginia’s newest rail line.

Public officials worry that its plans for a walkable urban community could be interrupted, at least for a time, if the station becomes a magnet for commuters from the outer suburbs.

The task force’s final recommendations — which are expected to go before the Fairfax County Planning Commission and Board of Supervisors later this year for approval — could affect the type and density of development near the Wiehle Avenue station and others, including Reston Town Center, that are part of the planned second leg of the Silver Line.

Heidi Merkel, senior planner with Fairfax’s planning division, said the task force anticipates concentrating high-rise development closest to the rail that would taper off a half mile away. Many compare the concept to Arlington County’s model: high-rise dwellings, restaurants and offices are clustered near the Metro line and then step down to neighborhoods with single-family homes. Developers are particularly eager to see how much density planners and elected officials will allow near the new Silver Line in Reston, with businesses hoping that the limit will be twice what it is now.

But overall, enthusiasm seems to be building fastest for the arrival of a system that has been on the drawing boards since the 1960s.

“I think people are eager because most of us, when we came here, came with the thought that there would be rail,” said Fairfax Supervisor Catherine M. Hudgins (D-Hunter Mill).

Mark S. Ingrao, president and chief executive of the Greater Reston Chamber of Commerce, said the business community has embraced the Silver Line and wants to see it go all the way to Loudoun. A survey this year of more than 400 business people by the Reston Chamber found that only 4 percent hoped the line would permanently end at the Wiehle Avenue station. The projected extension has played a large factor in the decision by Bechtel and other firms to relocate to Northern Virginia, county officials said.

“Of course, it’s going to be good for property owners,” said Patricia “Patty” Nicoson, president of the Dulles Corridor Rail Association. “But it’s not the property owners only that are going to benefit.”

At the Pica Deli, about a mile from the station on Sunrise Valley Drive, business has been slow for several years, with IT firms having cut back on catered events, owner David Kim said. He said he’s also seen little sign of activity connected to the new rail line, but he welcomes its arrival.

“I think it’s good for me,” the Springfield resident said.

At the station, Comstock Partners has already carted away enough dirt to fill RFK Stadium from the seven-acre site where the parking garage and other development will go, spokeswoman Maggie Parker said.

She said Fairfax has invested $83 million in the parking garage, which is a public-private project. The garage will hold 2,300 vehicles; there will also be slots for bicycles and a transit center for buses. In addition to the garage’s 11 / 2 million square feet of space, there will be 2 million square feet set aside for a hotel, residences, and retail and commercial office space. The tallest buildings will be 22 stories high.

Parker said that Comstock will follow through with plans to develop the hotel, office and residential dwellings regardless of Loudoun’s decision.

If anything, they would move faster to complete the project, she said. The firm also owns land near the last proposed Loudoun station. If Loudoun quits the project, Comstock will develop office space there.

“Everybody’s waiting and watching,” Parker said.