I think at this point, even if they brought him up now, DY would not qualify as a Super Two, so I don't think the arbitration clock should have any effect on their decision. My guess is that he'll get another couple of weeks, and if he's still hitting well, they'll give him 6 weeks or so in the majors.
Personally, I think the reason for the delay is that they don't want him to lose rookie status for next year. Having DY win ROY in 2006 would be something the Rays would market extensively. So giving him 200 PA this season, which would eliminate his rookie status for next year, doesn't help them. My guess is they bring him up so that he gets about 100-120 PA and is still eligible for the award in 2006.