New Gamescom information - X1/PS4 playable for visitors, Valve and Take2 attending.

Mega-Trends 2013: neue Konsolengeneration
(PlayStation 4, Wii U und Xbox One für Besucher spielbar), intensivere Spielerlebnisse, Cross-Plattform
Mega-Trends 2013: new console generation (Playstation 4, Wii U and Xbox One playable for visitors), more intensive gaming experiences, Cross-Plattform
The english press release doesn't have the info about the consoles being playable:

Valve attending (only in business area)

Valve also powers a "wave" event:
You can go wild on the gamescom wave powered by valve. It is in the outdoor area, but don't worry, you won't even get wet. A rotating carpet gives you the feeling of truly surfing a wave. The gamescom wave powered by valve is right next to the beach and extends the beach area with another highlight. Grab yourself a board and surf the gamescom wave powered by valve.
Take-Two attending

You can search for more exhibitors here:

Complete list can be found here:

Press information:

The infamous "New product database" is currently empty.
Valve will probably release some "Steam for PS4" thing as well, parallel to all the work they did around Portal 2's release.

Maybe we'll see a "[insert color] Box" SKU for next-gen with the Portals and Half-Lifes. I'd be surprised if they aren't interested in porting over TF2 or DOTA2 either.