Already paying for extra Docs/Gmail space? You're payment plan is grandfathered into Google Drive.

Google storage plans have changed, but you can stay on your current plan as long as you:

• Keep your account active
• Keep payment information in Google Wallet accurate and up-to-date
• Don’t cancel or upgrade your current plan

via support.google.com

This is good news. I can keep paying $5 per year for 20 GB instead of the $2.50 per month ($30 per year) for 25 GB that new Google Drive users will pay.