At some point between the 2003 I owned and the current lineup, BTB bodies did shrink/shift a little - they've got a smaller foot print, but larger and I think more aggressive horns. It's pretty subtle, but I think a great improvement.
Personally, I find the 6 and 7 string models look the best because the proportions of the wider fretboard fill out the space between the big horns better - I generally find the opposite is true on more conventional basses. For example, I think a 4 string P is nicer on the eyes than a 5.
The lack of a 4 string in the lineup isn't too surprising...these basses are Ibanez's ultra modern, boutique style offering, not something typically associated with 4 string basses. The Foderas, Roscoes, Beneventes, etc of the world put out way more 5/6 stringers than 4s.
The lack of a Prestige offering in recent years I find confusing though. In keeping with the boutique styling, Prestige workmanship/features/pricing seems like a natural part of the line. I think the only Prestiges currently offered are the SRs, though - I think the decision is some combination of a branding strategy, keeping the SRs are the flagship, and an operational reality - they may not be able to support two lines in the Japanese facility(s) producing the Prestige SRs. They've got guitars coming out of there, too. The reality is Fodera can charge whatever they want for a bass, but Ibanez is tapping out the Lorenz curve of it's brand loyalists by $2K.