Well what they write is correct its just cosmetic. Its just Pimp My Ride, new bells and wistles but still the old car underneeth. Its a pig with lipstic or however the expressions goes.
Nothing actually improves usability wise. Posting aint improved, media library aint improved, WP as an application platform aint improved. Improved theme viewer doesnt really matter to most users I think, Why? Because the need for that means you have A LOT of themes installed on your site and you switch frequently. And how many non wp.com users does that?

Improved theme engine and plugin engine would be good. Depency support, composer support and what not to really make WP a viable application platform. Such stuff would be great. If the big thing with WP is the plugins and themes then give the devs really good tools to work with.

@Chip Bennett - Most likely WP4 is WordPress 4.0. Essentially he is expecting that the core team will do something new and not just patch old stuff.