He is certainly progressing and staying competitive in the 15 (and to a lesser extent the 800), no doubt I agree with you on that. He won the past two US titles as you mention as well as making he '08 1500m Olympic team with his 3rd place finish in the trials. Moving up would be risky - he could miss out on opportunities at 1500m while trying to focus on the longer distances, and then if he tried to move back down to 1500 who knows if that would be viable. However I think the beneifits and likely success in the 5k outweight the risks of leaving the 1500 behind. Whether he runs inside 7:35 this week or under 3:30 later this summer I don't doubt he'll continue to suceed and improve, regardless of which event he makes his focus.