There is nothing to be happy with.
Debian have a release cycle that is not appropriate for bitcoin. As my experience suggests me,
bitcoin software were released very often in the past and often introduced changes with
When the next Debian stable is getting close to release, we can decide if we want to ship the version that is contained within the proposed release, or keep it out.
Also, there is a mechanism for updating packages in stable, its more strict, but if there were protocol changes that made the older version no longer work, it could be updated to support that.
Would it possible to incorporate ./debian directory into the official bitcoin source repository?
Isn't that a better option to support Debian (or to be supported by Debian)?
This actually does not help Debian, in fact it usually makes things more complicated and problematic. Please do not do this.