Do you have any evidence to support this? If not then this topic is pointless. They've had a team of 100 people working in full production for nearly 2.5 years. They waited to reveal the game until they had a deadline they were sure they could make. I do not think it will be delayed.
For all you doubters let me tell you this...
Oblivion was announced on September 10, 2004. At this time the game had been in development for roughly two years.
Oblivion was originally announced to be released in the Winter of 2005 (more than a year after official announcement)
Oblivion is delayed until Second Quarter of 2006.
Oblivion is released on March 21, 2006.
History is on my side, folks. Go ahead and bet against me, though.