I can't speak for the DS which is obviously doing extremely well, but since I purchased my PSP, I can't recall the last time I've even thought of playing a game on my PPC (granted I don't play the PSP that often either, but if I think of portable gaming, it's a no-brainer). I agree with all of the author's comparisons between the games on the two platforms (i.e. - there is no comparison). There would need to be some significant incentive for the big boys to pay attention to the WM platform and polish up the games that could compete.
I'm doubtful a WM-dedicated gaming platform will ever come. It's taken over 15 years for a Nintendo-competitor to even remotely compete against Nintendo on this level the way Sony is competing currently... and I don't see any company outside of Microsoft that could afford to take this kind of risk given that track record.
If there's any glimmer of hope, it's that Microsoft is the only major console gaming manufacterer who hasn't yet ventured seriously into the handheld gaming arena... so perhaps in the future, a portable XBOX could be discussed? I think it would take both Sony and Nintendo opening up a significantly larger market than what we see currently... and both companies would have to exhibit tremendous success before I think Microsoft would consider it.