Hi
First off, the page is still online. Unfortunately, it appears the link in Casper's post had become truncated at some point, and as such was missing part of the URL. The correct link is below.
http://online.ts2009.com/mediaWiki/index.php5/Trainz_Life-Cycle_Policy
In regards to the suspension of support for TRS2006 and older's access to the DLS after September, please see this post here:
http://forums.auran.com/trainz/showpost.php?p=591108&postcount=144
It is a long post, however it does contain a fair bit of information on some of the reasons of why we will not be supporting.
However, in regards to removing content, we have not finalized any plans regarding this. At this time, we will only be removing content if it either breaks the COC or the Terms and Conditions for uploads. In future we may remove content that is faulty, however we may also implement methods by which these items can be repaired as well (and hence would work in native mode in TS2009+). Items that cannot be repaired would most likely be removed, however these items would have an extremely high likelihood of not working in any edition of Trainz for most cases (scripts are a different case here). The preferred situation is that creators update/repair their own content, however this will not be the case for many items, and as such we are investigating different avenues of action that we can take here.
However, regarding content already on the DLS, nothing is yet confirmed, and as such the current policy regarding content (namely that it must abide by the COC and the Terms and Conditions for uploading) is still in effect.
Of course, new uploads for 04/06 at this time are passed through the same level of error checking as TS2010 assets (with the appropriate exceptions for legal tags for the older editions, such as the older 'bogie' tag format, based off the build number in the config.txt file). As such, these items would not be removed in the foreseeable future.
Of course, if we removed every single assets that was older than TC1 from the DLS on the 1st of September, then we would also have to remove many items built for the newer editions due to the number of these assets used by asset creators (including route builders, etc of course). This is not an action that we would take lightly, nor is it something that we plan to do.
This may, of course, change in time. However, at this time, this is the current situation on this matter.
Thank you