I wouldn't say "Everybody wants updates."
Personally, and I know quite a few people that feel the same way, if something works the way I need it to, I don't need an update for it.
Most software as it updates over the years tends to just add bloat to it. Some add useful features, and that is welcome. If it already does everything it was intended to do and everything the users need, then there is no need to do further updates.
A lot of software these days, however, seems to be released before it was ready, so that software needs constant updates to bring it up to where it should have been when it was initially released.
Windows 10 for phone's preview would be in the same state as Windows 10 for desktop was when it was initially made available. There could be more UI changes and internal changes that could change hardware requirement. We may even see the start screen UI change, who knows.
I think the first windows 10 phone preview will be much more stable than the windows 10 for PC. (Or at least it should). Users and Microsoft can not afford that a lot of devices will frees/brick or what ever.
So I do not expect a lot of new features in the first preview. But a step by step introduction.
You're putting what you want on the general population. Most people I know hate updates, "oh, another one! It works just fine how it is right now!". My family, for example, only updates their stuff so they can get rid of notification.