Scanslations are the final nail in the coffin for US manga distribution. Companies like Tokyopop were horribly mismanaged to begin with but the ease of access to and blatant visibility of sites like onemanga made buying manga foolish to any fan wanting to part with their money elsewhere. Onemanga's death won't spell the end of the scanslation scene, it'll just move back underground where it originally started. But I think the US manga market is bleeding a long slow death and is inevitably doomed.

They do this every few years to scare us back underground, they did it for anime and now manga. Give it some time and sites will pop up again and not to mention there are still a ton of sites. Honestly the more popular the series the bigger the chance of it getting taken down, so thats why one piece, naruto, bleach etc are being targeted. So while the popular series might get taken down there are still plenty of other series that are left to be found and enjoyed. I think onemanga overreacted by shutting the whole site down honestly but that was their decision.