For Ducati to buck tradition and even think about an alternative to the trellis frame is a big deal. It would indeed be a shock if they came out with a street V4, but the precedent has been set eventhough for now the V Twin is apparently safe due to displacement/power increases since the 1098 release. They won't make the changes unless they are up against the wall

like they were in MotoGP and close to it the last couple years of the 999. The trellis is still viable for years to come, both on the street and track.
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2003 HD FLHRI
2003 Ducati 999R #189
2009 Buell 1125CR (sold)
2007 Ducati 1100S MTS (sold)
2005 Honda 600RR (totalled)
2001 Ducati 900SS (sold)
1995 Ducati 916 (sold)
2004 Ducati 999S (sold)
2005 Honda 600RR (Oops, I did it again, this time in red/black - sold)
www.ducati-owners-group.com