They wouldn't release Itami.
He definitely lost a lot of the shine he came in with...but he'll be back. And Itami vs Nakamura would be a barn burner. Anyway, Itami and Nakamura are vastly different talents. People need to stop drawing comparisons just because they're both Asian. That's like saying "We don't need Apollo Crews because we have Shelton Benjamin".
I know that they're different talents, but with how WWE has treated Asian talents in the past it's not too out there.
Remember all of those reports of WWE looking for their next big Latino star? There are markets for that. Rey Mysterio, for example, was WWE Mattel's 2nd biggest seller right under Cena. WWE left a lot of money on the table with Rey leaving and that's why they were desperately trying to replace him.
With Itami/Shinsuke, it seems like WWE is trying to bridge the big Asian superstar market, but Shinsuke has a much more magnetic personality than Itami and he can supersede that and legit be a big star regardless. Everything about Shinsuke is appealing to the American audience.
It sounds weird, but this stuff does exist and WWE profits from having certain superstars. Like Khali and the Indian market that we always joke about.
It sucks for Itami because when he was signed, WWE was still changing everything about people who came in. If he came in now, he'd get to be KENTA from NOAH and would have been much better off.