Maybe she wanted to include English and wanted to dance in her music and PVs all along, but she saved all those for something that'd shock everybody in one big bang.
And the album, Rainbow, is that bang.. different style music, incorporation of English, dancing in a video, putting out a 40 minute music video, the incorporation of all these extras... I wonder what else she has up her sleeve.
She does a pretty decent job of English though.. I understood her without reading any lyrics. She's tons better in terms of English-speaking skills than Kuraki Mai, who I have to look at the lyrics in order to understand...