Well, it's not much more expensive for them to put it on PSP if they do a Wii version. Same with PS2. For some games, the last-gen versions will be worth it, for others they won't. Overall I daresay the math works in their favor. But the version they expect to actually make serious money, and invest accordingly? Surely that's going to be the 720p-plus version at this point.
I'm not saying this is their best strategy overall to make money, but as DC says, at this point, with hard evidence of low sales of the likes of Boogie in hand, they have to be realistic about their ability to create brand new franchises that would work on Wii/DS. They can't suddenly wave a magic waggle wand and say 'Thou shalt create million-selling non-games' and see all their teams just crank out tripe that sells. Just as they can't tell a team to go create the next WoW and get 10 million subscribers. That's always going to be a wild punt at a moving target.
So their best option probably is to continue to supply 'hardcore' games on the HD platforms.