Dupont Circle resident David J. Mallof proposed the idea back in November, and has now sought the requisite sanctioning by the federal government. Mallof went to the Feds in early April and got a sit-down with James Oberstar, chair of the House of Representatives Transportation and Infrastructure Committee - apparently the Feds are not opposed to the bridge (no Ted Stevens jokes here, please), but won't do anything 'official' until the DC Council and Mayor Fenty support it. The Council won't approve without some show of public support for the project, so the next step is for a public hearing. If supported, the Council would only need to earmark 20% of the overall cost, with the feds potentially picking up a generous 80%. This puts the timing of the bill at least into next year, because it will be nearly impossible to get the financing inked into the new budget by budget deadline of June 3rd.
If it gets that far, it will still have to go to the Washington Council of Government, which is chartered to oversee multi-jurisdictional issues. In this case, WCG would be mediating between the federal government, the DC government and the Virginia government, because a second bridge would then connect the island to Rosslyn, Virginia.
The proposal is to connect the land in front of the Watergate Hotel to Roosevelt Island, then across to Virginia. Mallof chose the Virginia location to connect the bike paths that nearly converge in the area, and proposes that the bridge could not only provide recreational use, but also serve as a main thoroughfare for sweaty commuters biking in from Virginia, who currently have a more complicated route after crossing Key Bridge, which involves either descending stairs or threading Georgetown's traffic, though even at this location bikers would still have to face a series of frogger-like challenges to get to the Mall. Still, some are concerned about the visual obstruction down the river, which has few open vistas thanks to the series of vehicular bridges.
Aside from the practical uses, Mallof stresses that the park falls within DC's perimeters, not Virginia's, forcing DC residents to cross the Potomac and park their cars on Virginia soil in order to take advantage of their park. Roosevelt Island remains so lightly trafficked, thanks in part to its inaccessibility, that it still boasts a mature white-tailed deer population.