I personally think this is a great move.
Scion was born when Toyota was still rather old, stodgy, outdated and struggling with younger consumers - the late 90s and very early 2000s. After Scion's introduction, Toyota injected better styling into all of their products, new engines and powertrains, "SE" trims for nearly everything, etc.... and they quickly became less boring.
Some of Scion's qualities weren't all bad, like the pure pricing strategy, but the brand's original core mission was no longer relevant very shortly after it was introduced.
On top of that, I also think Scion was horribly managed. What was originally promised to be quirky, fun new models every 2-3 years ended up being outdated Toyota products on 6+ year cycles.