Check out the Gmail blog and the companies efforts in their "Infinity+1" storage plan - a plan to provide Gmail users with "more space as we were able." According to the blog, the Standard and Education Edition storage, which is now at 2GB, will get a bump and begin matching Gmail's counter. Premier Edition users get bumped up from 10GB to 25 GB. The standard edition is free and the Premier edition is $50 / user account / year. The Education Edition also offers 2GB but makes the text-based ads alongside email, found in the Standard Edition, optional to students and academic faculty and staff.
Yahoo’s unlimited storage product provides unlimited email storage space. According to Yahoo:
Yahoo also offers the Yahoo! Briefcase that provides up to 30GB of free file storage free to Yahoo account holders. Briefcase is great for students who are accessing computers in different locations - imagine a community college commuter student using a computer at home and another computer at school. Brifcase allows file storage that can be accessed from both locations.
There have been Google Gdrive storage rumors for over a year now.