Disagree. I see three types of people we have to support:
A) Someone simply upgrades the WAR and continue use their old configs. They will get a deprecation warning in the logs but else everyting is as before.
B) Previous Solr users who wants to upgrade config properly. They will clearly see the new preferred config, and if they use it, they are ready for the deprecation without surprise. Or they may copy/paste own customizations with indexDefaults if they choose.
C) Totally new to Solr. Version 3.6 is their first download and they get it all right - with less confusion - out of the door, no surprises in 4.0.
This is how config deprecations should work in my opinion. No need to advertise to new users the use of a syntax that we want to go away. It would be more confusing for the C) people to see deprecation warnings being printed OOTB from their brand new search engine without knowing how to fix it..
What lacks in the patch is fixing all the other variants of solrconfig.xml all around the place..