Those of you who think Apple can't drop DVD and HDs at the same time - you haven't been around long, have you? Apple has a long history of being the first to drop obsolete tech.
I'll make the case here:
1 - DVD/CD - this is a given. It's so trivial hardly worth spelling out here. DVDs and CDs are not needed in 2011 - the Mac App store removes the last reason to have them, installing software. A DVD will not be built into the next MBP - end of story. I personally can't believe they've waited so long - I haven't used my DVD drive in 2 years, and have actually replaced mine with an optibay SSD. Those who still use them for whatever reason - get an external drive.
2 - SSDs. I think there's a case to be made where 256GB is "enough". Sure you can use more if you are working in some fringe area of computing - but then you can probably shell out for a 512GB or even larger SSD too as you are a professional and use the computer for work.
The only other reason to use more is gigantic music collections or wanting to carry your 4TB of pirated movies around everywhere you go. Apple figures people don't generally want to do that, and I tend to agree. I watch movies once, then move them to external storage - but I realize I might as well delete them as I never watch them again for the most part.
If you give up on carrying large movie collections around, 256GB is enough in the same way 16GB is simply enough for an iPod. Apple knows this full well as their smaller capacity iPods vastly outsell the 160GB HD based model - nobody needs to carry around 3 months of continuous music, even if they have that much. A few days worth is plenty - and even the smallest capacity Flash based iPod can do that.
It's the same for computers. I think 128GB is a bit tight, from personal experience - my music, images, and maybe a few movies and apps easily exceed that. But 256GB would be enough. That would leave me with all my music, all my pictures (which I must say is a bit pointless to carry around - how often do I look at 10 year old pictures? never!), and the odd movie / series I want to still watch.
My estimate is based on practical experience with my 80GB SSD - it's tighter than I thought, just work, apps, and documents, email etc, take up around 70GB on my system. I have all my media on the 500GB HD, pictures, movies, music. I like to keep all pictures and music with me, not because I constantly use them but because it's easier to manage this way. But video, I really don't need to carry that, and I wonder if I even need to store it anywhere - I like to collect, but let's face it, anything I have I could always re-download. It's all stored in the collective that is the internet already.