On what do you base this theory? I agree that the days of the Challenger are numbered, but I would be surprised to see it gone that fast. 08 was only half a year, and only SRT. 09 they were still backed up with orders when production was interuppted due to bankruptcy. I would be amazed if they didn't try selling the thing for at least a full year of the whole model line.
Future after the '10's is quite uncertain. If the '10's are selling well, maybe we see 2011, but I doubt anything after that. Pretty sure we won't see a second generation or anything. Especially with Fiat's apparant anti-V8 mentality and looming higher CAFE requirements.