Hall will probably get around to another track segment or two at some point in his career.
It seems that he's been ticking off a lot of marathon competition-related goals:
1) race a marathon competitively (London 2007)
2) race a marathon fast (London 2008)
3) compete in the Olympics (Beijing 2008)
4) trying to win a major marathon (Boston 2009)
After accomplishing these goals, it will be time to evaluate where he stands, and what he needs to do to improve on being 5th at London and 10th at Beijing.
The fact is, Hall got dominated by Wanjiru etc. at Beijing. He needs to find a way to race them and not get dominated. Perhaps doing so in the world athletics champs 10k or a big half-marathon (GNr, world half champs) is a more realistic proposition than doing so in a marathon. After all, 59:30 in a solo effort is only a minute off the world record! If he could get in a half-marathon race against Wanjiru/Tadesse/Merga/etc. and show he is podium-class that would definitely be a step in the right direction.
It would be great to see him do that in a track 10k also. But is that really realistic? He'd have to essentially run his current 5k PB back-to-back. Not saying he can't do it. But I find 59:30 in a solo effort much more encouraging than 3:42/13:16 after years of focusing on those events and running them in high-caliber meets.
Hall may just not do well with the environment of track racing. I know guys like that at a variety of levels. Like I know a guy who focuses on the marathon; one time he won a 10k road race in 31:10. But on the track he has only run 15:07/32:21. Based on his road time he really wants to get in a 'get-in-line-and-PB' 10k race and go for a sub-30:30, because he's trying to run a 2:19 marathon and most of the other guys going for that can run 29:30-30:30. But he also knows that on the roads he just rolls a lot better. He can cruise through a 15:30 5k split on the roads without feeling too tired; on the track he's had 5k races where he can't break 15:30.