The new generation of MBPs will be ultra-thin with no more optical drive will vanish and no more spinning hard disks, either. With cloud storage and applications becoming more and more popular nowadays, Apple is slowly making CDROM's a thing of the past.
Moreover, with a flash-based storage - the new line of laptops will have longer battery life and faster reading and writing data speeds.
Old MacBook Pro owners need not fret however, as many say that Apple will not be totally changing the whole line at once, but instead slowly shift the design in every release. So old users will not feel so left out when the new models come in. It can be remembered that the company did this pattern with its transition to the present unibody design back in late 2008 and early 2009.