Clay Bavor, of Google:
Life gets a bit easier when your Google products work well together—whether that’s inserting a Drive file into an email or sharing a photo from Drive on Google+. As this experience becomes more seamless, separate storage doesn’t make as much sense anymore. So instead of having 10 GB for Gmail and another 5 GB for Drive and Google+ Photos, you’ll now get 15 GB of unified storage for free to use as you like between Drive, Gmail, and Google+ Photos.
Very smart update. The great thing is that if you don’t use Google+ or Drive, you now (theoretically) have 15 GB of Gmail space.