The Kobo Arc is intended as the replacement for the Vox, and overall it looks great. Twice the clock speed, lots more RAM, and many other advantages. So am I going to replace the Vox with it? Likely not. I might replace my Vox with the new Kobo Glo (front-lit e-ink e-reader), actually.
Unless it's an oversight, there's no mention of SD card support in the Kobo Arc (it does mention SD card support for some of the other new e-readers, which increases the odds it's not an oversight).
And the idea of an e-ink reader with a front-lit option is kind of appealing. We'll see if I can live with the slower screen updating versus a tablet.
But I want a Windows 8 tablet anyway, and that's more appealing to me than an Android tablet, so I'll just use the Kobo app on that for times when I'd prefer a tablet over e-ink.