If Ferrari didn't know before they will now, trying to force Rossi's hand always ends in a bad way. Attempting to restrict or confine Rossi is something he doesn't take very kindly to. There were many reasons for his leaving HRC after 2003 but I can assure you lack of freedom was one of them. He nearly left the factory prior to 2002 due to sponsorship issues. HRC insisted that he, being a factory rider, ride in Repsol colors. Rossi insisted that he, being a free spirited factory rider and all around moto God, ride in whatever colors he chooses. Rossi finally backed down and agreed to be a Rpesol rider and keep his Nastro Azzurro money to a personal thing but it certainly didn't make him look at Honda in a better light.
If Ferrari are trying to force him to do something he may decide to go along, I'm not saying he will or won't sign for Ferrari by 2006. What I am saying is if he does decide to do so and should he become a competitor, this deadline is not going to make Rossi think any better of Ferrari. He says he's had other offers from F1 teams, he may just take one of those up instead of Ferrari and give the scuderia the big fck off.