am not saying PPA is bad just worried about not to lose the magic of debian who has everything in one place.
This is already the case. Not everything I package deserves to go into Debian main. e.g. because it is specific to a problem I am solving and may not be of general use. Or because of problems with licensing, Or because it has changes that the Debian maintainer disagrees with. Or any number of other reasons. However that does not mean I want to make the package private. It is possible that others may be able to make use of it. Who knows, maybe at a later date it might be ok to put in Debian main.
PPA support will allow keeping more things open. Instead of requiring developers to create their own private repositories on random websites, everything can be in one global set of repositories.
While it may be true that some deserving packages live in Ubuntu's PPA forever, I am sure that there are deserving Debian packages that are stored in random private repositories for ever. PPA support for Debian wont change this - although it may make it easier to migrate from the PPA to Debian main.