Sony's redesigned Vita is slimmer and lighter than the original. However, the new model drops one of the most well-received features of the original system: the OLED screen. Instead, the upcoming system uses an LCD screen.
There are numerous reasons for the switch. Sony points out that using LCD makes it easier to make the system slimmer. However, it's also cheaper, which LCD providing a better yield rate.
Unfortunately, an early look from Japan would disagree with that assessment. In particular, color reproduction seems to be significantly affected by the switch to the cheaper panels.
No US release of the Vita-2000 has been announced yet. However, Sony recently dropped the price of the OLED-equipped Vita to $199.