As the world speed record set by the Japanese maglev in 2003 is 581 km/h, despite all low-key formulations by SNCF and Alstom officials, I think inofficially they are eyeing that threshold...

But I'd hope these tests also make practical sense, as an extreme test of the technology of the next generation of TGVs (chiefly: at last switch to distributed traction [a first in high-speed Jacobs, that is between-the-cars bogies], that with the next best electric motor type [permanent magnet synchronous] and state-of-the-art power electronics [IGBT]).

_{*Lunatic*, n.
One whose delusions are out of fashion.}