McMurray in the #97 instead of #6?

here is a new one….from the Tampa Tribune: When Jamie McMurray [current #42 Texaco driver] joins Roush Racing in 2007, he may drive [Kurt] Busch’s #97 Ford rather than Martin’s #6 Ford as originally planned, Roush said. McMurray is scheduled to join Roush in 2007, after his contract with Chip Ganassi Racing expires. Busch is leaving no later than 2007 to take over Rusty Wallace’s #2 Miller Lite Dodge at Penske Racing South in 2007. Busch’s contract with Roush runs through next year.(Tampa Tribune), if so, what is the point of Martin staying another year?(9-13-2005)