FWIW, I think I may have solved the mystery why some of us legacy users have not been notified.

http://googlepress.blogspot.com/2006/08/google-launches-host...

"A standard edition of Google Apps for Your Domain is available today as a beta product without cost to domain administrators or end users. Key features include 2 gigabytes of email storage for each user, easy to use customization tools, and help for administrators via email or an online help center. Furthermore, organizations that sign up during the beta period will not ever have to pay for users accepted during that period (provided Google continues to offer the service)."

The original version of the TOS from August 2006 read as follows:

https://web.archive.org/web/20061029132431/https://www.googl...

"16. Modification. Except as provided in Section 17, Google reserves the right to change or modify any of the terms and conditions contained in this Agreement or any policy governing Google Apps, at any time, by posting the new agreement at http://www.google.com/a/help/intl/en/admins/terms.html or such URL as Google may provide. Customer is responsible for regularly reviewing any updates to this Agreement. Any changes or modifications to this Agreement will become binding (i) when made in a writing executed by both parties, (ii) by Customer's online acceptance of updated terms, or (iii) after Customer's continued use of Google Apps after such terms have been updated by Google."

"17. No Fees. Provided that Google continues to offer Google Apps for Your Domain to Customer, Google will continue to provide a version of Google Apps for Your Domain (with substantially the same services as those provided as of the Effective Date) free of charge to Customer; provided that such commitment (i) applies only to End User Accounts created during the period when the Google Hosted Services are considered a beta service (the "Beta Period") by Google (such Beta Period determination at Google's sole discretion) and (ii) may not apply to new opt-in services added by Google to the Google Apps for Your Domain in the future. For sake of clarity, Google reserves the right to offer a premium version of Google Apps for Your Domain for a fee."

In mid 2007 the language was changed to read the following:

https://web.archive.org/web/20070407174217/http://www.google...

"17. Modification. Except as provided in Section 18, Google reserves the right to change or modify any of the terms and conditions contained in this Agreement or any policy governing the Service, at any time, by posting the new agreement at http://www.google.com/a/help/intl/en/admins/terms.html or such URL as Google may provide. Customer is responsible for regularly reviewing any updates to this Agreement. Any changes or modifications to this Agreement will become binding (i) when made in a writing executed by both parties, (ii) by Customer's online acceptance of updated terms, or (iii) after Customer's continued use of the Service after such terms have been updated by Google."

"18. Fees. Provided that Google continues to offer the Service to Customer, Google will continue to provide a version of the Service (with substantially the same services as those provided as of the Effective Date) free of charge to Customer; provided that such commitment: (i) does not apply to the Domain Service described in Section 4 above; and (ii) may not apply to new opt-in services added by Google to the Service in the future. For sake of clarity, Google reserves the right to offer a premium version of the Service for a fee."

This version was persisting thru at least March of 2011:

https://web.archive.org/web/20110330181415/http://www.google...

However by December of 2011, that language was gone:

https://web.archive.org/web/20111231230542/http://www.google...