At least for the regular S.A. voices, they are not used in styles, only for accompaniment. The two reasons the T3 styles don't sound good in the S910 are 1) that they have a lot of other voices, Mega! Voices and many of the Sweet!, Cool!, and Live! voices that are not in the PSR-S910, and 2) the T3 has New Guitar Enhance Style File Format (GE-SFF) which improves auto-accomp Styles.
The PSR-S910 will have the Guitar Enhance Style File Format, something which the T2 didn't have. The question is whether this was one of the reasons that many of the T3 styles don't load properly on the T2. Is the T2 or S900 equipped to play these style files?
The S910 will have a lot of voices that the S900 didn't have, so many of the T3 styles will probably load into the S910, but I am betting that there will be many T3 styles that take advantage of the close to 100 Mega!, Sweet!, Cool!, and Live! voices that the PSR-S910 doesn't have.
I don't think that Yamaha will make these styles available for the PSR-S910, but I bet that there will be some industrious people among us who will convert them.
Beakybird
[This message has been edited by Beakybird (edited 07-30-2009).]