Sure, they have... it's called the Evo III. They kinda went backwards with this model, starting with a racing chassis and basing a tub model around it.
They may release a carbon chassis specifically for this one, but it's very doubtful. They just needed a newer shaft drive platform for their aging TB-01 and TL series, and this was the most viable solution since most of the parts were already available.
It won't be brought much more forward than this, I believe.. the TA05 is their new baby, and is a totally new platform altogether. You can tell they put quite a bit of effort into making it, so I think that'll be their new focus for their future TRF upgrades.
And, like Ghostfit said, there's a lot more popularity with high-end belt cars than shaft.. The Pro 4, Evo IV, SD, and TC4 are pretty well it, and only one come to mind when it comes to still being in the racing limelight. Also, look at the recent TCS.. the top 3 GT2 guys had TA05's..
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