Power does not define generations. It's an upgrade to an existing console with an existing library.
Turbo-Duo was not a next gen system. It was a mass upgrade. PS2 slim models with a faster CPU is just a upgrade.
Sega Wonder Mega was not a next gen system but a upgrade. Game Boy Color was a upgrade. Same with GBA SP to GBA. Same with DS light to DS or DSi to DSL. New 3DS to 3DS. PSP 2000 as to PSP. All just upgrades.