Rumors abounded, speculating Rossi would switch from two wheels to four wheels some time after 2008. Initially these rumours centered on Rossi switching to Formula One and his test drives of the Ferrari F1 car received heavy media coverage.

Most recently Rossi tested the Ferrari in 2006 on January 31, February 1, and February 2 at Valencia, later in 2008. The first test saw Rossi spin out on the damp track into the gravel trap, ending his day. On the second day, he posted the ninth fastest time of fifteen drivers, approximately one second behind Michael Schumacher, who himself was third fastest. Rossi lapped faster than seasoned drivers Red Bull Racing's Mark Webber and David Coulthard and Toyota F1's Jarno Trulli.[13] On the final day of testing, Rossi was just a little more than a half second behind Schumacher's best time.[14] Schumacher hailed Rossi as having immense talent and said he would be perfectly capable of moving to Formula One and being competitive immediately.

On May 24, 2006, Rossi announced that he would be staying in MotoGP until he felt his work on the motorbike was "finished." Ferrari driver Schumacher said that he felt "saddened" by Rossi's decision but supported it. Rossi subsequently signed a new contract with Yamaha for the 2007 and 2008 seasons, then for 2009 and 2010. The two-year contracts were notable as after leaving Honda at the end of the 2003 season Rossi had refused to sign contracts of more than a year.

Beyond his interest in F1, Rossi's strong passion is for rallying. His first official foray into rallying came in 2002 at WRC Rally Great Britain, in which he crashed out on the second stage (first non-superspecial stage). He subsequently raced a factory Subaru Impreza car in the Rally of Monza in November 2005.

On October 11, 2006 it was announced that Rossi would enter that year's Rally New Zealand, a WRC event which was to run from November 17-19.[15] He competed in a Subaru WRC car finishing 11th out of 39. On November 26 2006 Rossi also won the annual Monza Rally driving a Ford Focus WRC car. He beat the 2005 rally victor Rinaldo Capello by 24 seconds, winning five of the seven stages on his way. He also managed to outpace former WRC Champion Didier Auriol by seven seconds in the head-to-head Master Show final. Rossi also announced at the 2006 Monza rally, that he would be entering the 2007 Rally of Great Britain, however, he later opted out. At the 2007 Monza Rally, Rossi again took first place.

Rossi has been linked with a move to both Formula One and the World Rally Championship in the past 18 months, having tested for Ferrari and competed in a number of rally events.[16]

But Rossi decided to remain in Moto-GP; "I have a contract with Yamaha until 2008," said Rossi. "When that finishes then we will see. What I am sure about is that I will ride until I'm 31 or 32 at most. I will look for new stimuli in the next few seasons, but for now I am fully motivated."[17]. Rossi signed a new two year contract confirming he will be at Yamaha until 2010.[18] He originally planned to use the Impreza WRC2008 during his participation in the Rally GB in December 2008,[19] but decided to drive a Ford Focus WRC instead.[20] He finished the rally in 12th place, 13 minutes and 20.4 seconds behind eventual winner Sebastian Loeb.[21]