I don't think so.
The recent Encores are getting bigger (Omega & Metroplex) & I'm pretty sure a TakaraTomy feasibility study would find that the demand would be very high amongst the adult TF customer base, more than justifying production costs (as long as the final price isn't too high).
99% of the mould can be borrowed from the recent Car Robots line so all that's left to say is... PLEASE!!! :)