With the right song and the right time...

[jewelbox]

Promotion could be the key in here, but honestly I think it's mostly about the image too. Ultimately, she can continue to do her thing, but public eye doesn't see her anymore like they used to. New generations, new potential fans should be also considered, if she wants to sell more. That's why I think PQ covers were Fail.
I've heard that japanese really do consider Namie "cool", but Ayu as "old and uncool", kinda sad.
She should do something to her image, starting with clever PR in order to sell more.