Plasma 5.0 has been released today, but the work does not stop with it.
We have been preparing features planned for 5.1 (and later) for some time now. The new activity switcher is one of them, and it is coming along nicely. It is already much more polished and optimized than the one available in 5.0.
If you want to see it in action, just check out the new screen-cast (I recommend watching it in 720p, it looks much nicer):
It shows some old features, but also a few of the new ones.
Be seeing you!