Thanks for your friendly reply.
Yes, the issue (or rather: paradigm) you mentioned is clear to me - and I value anonymity and the de-centralized approach. But there are a few points that I would like to say about that:
1. Such update feature / notification feature should NEVER be mandatory, only optional for the type of User I mentioned who will gladly give up part of anonymity for convencience / peace of mind
2. The network itself will remain de-centralized. Most coins already have a centralized approach when it comes to software-distribution, though: GitHub or their homepage. So an autoupdate-feature would not change that
3. if the wallet actually only transfers the eMail-address + the QT version (and not addresses etc.), the anonymity is not much less than in e.g. this forum. Many people use their real names (I do, for example), many post their addresses, some use their regular eMail addresses etc. I am almost sure that if somebody would do a big datamining trying to find personal information on a given user account (whose coin address is known because he used e.g. a giveaway thread), he would most likely succeed. So in theory, Cryptocoins can be anonymous, but in real life they are rather pseudonomous. And even that is weakened by every piece of information users leave of themselves in the www. So such notification feature doesn't really change much here - as long as (1) remains valid.

Thanks again