Currently, the only options for getting across Aurora to go to Uptown / Lower Queen Anne from South Lake Union as a pedestrian is to walk along a 3-ft. wide strip of sidewalk on Mercer – not fun – or walk down Denny to 5th – also not fun.
If the South Lake Union neighborhood can glean something positive from the decision to replace the Alaskan Way Viaduct with a deep bore tunnel, it’s that it accomodates a lowered Aurora. Under this configuration, east-west streets such as John, Thomas and Harrison would connect over Aurora. A lowered Aurora was once included in the 2-Way Mercer plans, but stakeholders eventually backed away from the $200M upgrade and supported surface-level intersections on Aurora instead. The prospect of stoplights on Aurora was a contentious issue with the freight industry who would’ve battled to keep their highway unfettered.
Now that a tunnel has been chosen, Aurora can work for both the freighters zooming below and pedestrians crossing above. And lowering Aurora is no longer an added expense because the tunnel has to rise up to the surface gradually anyway.
As mentioned in a previous update on 2-Way Mercer, the design on the north portal is still up in the air as far as ingress/egress goes, but transportation officials seem committed to reconnecting the grid at Aurora. SDOT’s people say Mercer itself will continue to run underneath Aurora, but the cutout will have to be larger due to the widened street and sidewalks.
Here is a diagram that was included in the tunnel proposal which highlights the crossings over Aurora:

It will be nice to be able to visit our friends over in Uptown / Queen Anne, but it’s still going to be a long while. Aggressive estimates put the completion of the project at 2015.