[Swede]

That section of the ring motorway is likely to get built, sadly it'll get built after the huge western bypass (20+ km of 3+3 lane motorway - all in a tunnel! + on & off ramps that stretch for many km). IMO the obvious thing would be to first build the East Link, then if the need for motorways still ranks above decent urban planning they should go for Diagonal Ulvsunda which is of far greater use and wouldn't lead to as much sprawl.

source

Getting that rail tunnel built at the same time should IMO be a basic requirement for the tunnel to be built at all.
Having LRT (Tvärbanan) going in a ~75% circle around the inner city (it's already today about 50%) will spur people to call for closing that circle. The connection Ropsten-Waldermarsudde-Sickla itself probably won't have much traffic at first. But connect Ropsten to Universitetet and on to Solna Station and the relief to the Red subway will, is my guess, be significant. As will getting areas now outside the Inner City to be thought of and used more as part of the core.

Yeah, since '06 things have been changing. The biggest change is coming on-line in a couple of years though: Citybanan! the commuter trains getting re-routed into a new tunnel under the inner city with the off-ish station Karlberg being replaced by a new station under Odenplan with direct transfers to the Green line subway (and far, far better connectivity to inner city buses).

try going this time of year next time short days, cold, windy and wet. :/

Ah...
Slussen...
Work has begun!
One building in the middle of that proto-cloverleaf is being torn down right now. I'll make a post copying my thread-start in the Stockholm SSC subforum. It's not really that focused on transit, but it IS a very important transit hub.