I doubt it. Marshall's not stupid enough to ignore Slash's marketing powers. They're going to price it to the LCD of his guitar playing fans (well, as much as possible.) I see it being 4-600 depening on features.
My guess, $699-$899
Marshall went of the rails with pricing a few years ago.
$699. That's on the high side of reasonable, in my view. Looks like a Slash-i-fied Class 5 with digital reverb.
http://www.guitarhangar.com/marshall-sl-5-slash-signature-amplifier.html
That's about twice what I'd realistically consider paying for an amp like this. Marshall needs to take a hint from Fender and the Excelsior.