The list of companies present include Square Enix, Capcom, Sega and Sony Online Entertainment, among others. However, how Pocket Gamers managed to obtain "top secret" information makes this very suspect, not to mention SOE's presence, who would likely only show up as reconnaissance for Sony's own handheld, the PSP. The article further claims that another two-day workshop is being planned in Madrid to show the new N-Gage to European companies and that Nokia will publicly unveil the new handheld at this year's Game Developer's Conference.
Noting that Nokia had an E3 2006 booth showing off some N-Gage titles, despite abysmal sales, it is plausible that the phone company is working on N-Gage 2.0 and is looking to garner some third-party interest; however, we don't want N-Gage fanboys (population: 3 or 4, maybe) to look at this story as definitive lore. We'll see if anything new comes our way leading up to GDC.