Agreed, in this day and age we mostly don't have or use the ISP services that come with our connections.
Would you then use a Mozilla run mail service similar to gmail complete with calendaring and document storage, all built into a suite of client apps ?
I think for a certain demographic this could turn into a good Google competitor if done right.
Although a great 'client' experience is absolutely crucial for Firefox Premium's success and would be a modern resurrection of Netscape Communicator in that sense, what I mostly need is convenient 'servers' from a company that I can trust and a business model I can support. In a sense that would be a modern way of meeting the needs of Netscape Communicator, sure :)