Now that it's all but confirmed, I'll give my 2 cents.
This is fucking smart, only because they doubled the ram so late in launch game dev cycles. Before the upgrade theyhad 3.5 GB and seemed to be doing fine. Now with 5.5 GB they can go balls to the wall compared to their origional plans. Having 1.5 GB more would be pointless apart from lazy devs who don't want to optimize and/or get rid of loading.
Leaving all this extra ram allows Sony to answer this tough question of game vs os after it is on the market. If in a year they decide to cut the OS by a GB, games in dev will be only jumping from 5.5 to 6.5 which again doesn't scrap their work.
It's also nice how game ram shrinks like on Vita. Maybe they will at first add another gig to this. I'd expect the xbone to do something similar, but do we know how much the game ram shrinks by? If it shrinks by 3 GB for example, two full games could be on system at the same time.