I agree with you Benzy, except that the n55 is not completely on the same timeline as the n54. The piggies are way more advanced than ever before and porting the development over to n55 isn't such a huge time lag as before.
In the other hand, flashes are more involved with the cars' firmware and versions which is one the major complications for them. Tuning for a big single is far off for them because as you said, they are only now beginning on the base maps.
Vishnu has already been hinting that they were test fitting their big single on an N55 which speaks volumes for the current piggies being able to handle it. Maybe in addition to the fuel trim flash being done on the n54 now.