Also, I was wondering where such a decision was made.
The new Talk code was requested both on Village Pump and on the mailing list repeatedly. The user page stuff was simply a side effect of that. However, if you want to keep up with the latest changes and possibly have some influence, check out the code and start hacking.
http://meta.wikipedia.org/wiki/How_to_become_a_Wikipedia_hacker
Regards,
Erik