Bearing in mind that the launch is due in the first half of 2007, five to seven smartphones could well mostly cover S60 3rd Edition models that haven't been announced yet, as they're often unveiled just a few months before entering production.
As Pocket Gamer point out, the N93 does seem a likely candidate to be one of the compatible phones as it has been used to demonstrate Next Gen games, has an optional landscape mode and contains a 3D graphics chip. And, as several AAS readers have pointed out recently, Nokia's latest firmware has fixed the N93's multiple-button-press problem so it can now be used properly with games.
The other likely candidate that we know about is the N95, which was announced some time ago and is due for release in the first quarter of 2007. It too has a 3D graphics chip, and it too can be used in landscape mode.