I think it says the old system will be staying and you can turn on email notifications for the messages 

I'm just wondering, knowing GS, if at a later date they will shut off messaging emails (with the full message in it), keeping it all 'in house' under their control and this new messaging is the start of this process and all you'll get is an email saying you've got a message but no content, forcing you to login

as I said:

or am I just being cynical

PS: They stopped sending the My_Caches gpx update via email and you now have to login to get it - a right pain