We are already at E5 in most fuel stations. A DoT report last year raised serious concerns about the effects of E10 on any vehicle over 5 years old.

http://www.realclassic.co.uk/techfil...fuel_study.pdf

special note to page 25;

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Triumph, all Triumph motorcycles have been compatible with E10 since at least 1994. From 1993 to 2008 nylon moulded fuel tanks were employed but due to vapour permeability concerns a switch back to steel tanks was made [96].
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BMW. BMW motorcycles have been E10 compatible for at least twenty years [107].
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Harley-Davidson. All motorcycles have been E10 compatible since the 90s [108].
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Kawasaki. Kawasaki Heavy Industries are still considering the effects of E10 and do not recommend its use [109].
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KTM. All models from 2000 are compatible with E10 [110].
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Yamaha. All models are compatible with E5 and some new models are compatible with E10 [111].
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Suzuki. All models have been compatible with E10 since 2005 [112].
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Honda. All models have been compatible with E10 since 1993 but carburettored vehicles could suffer poor drivability [164, 165].
and the conclusion on page 74;

Vehicles ten years old or older, carburettored vehicles (including powered two wheelers) and first generation direct injection spark ignition vehicles should not be fuelled on E10 unless the manufacturer can state the vehicles are compatible with E10.
The automotive industry should produce a comprehensive list of vehicles compatible with E10. While it is acknowledged that some lists do already exist if in doubt the vehicle operator should seek clarification from the vehicle manufacturer.
E5 should not be phased out in 2013, its widespread availability should continue for the foreseeable future.
Consideration should be given to maintaining a specification for E0 fuel for historic and vintage vehicles.