"Support" for XML is really defined by the end-user's "browser". To get XML working if your game you would have to write your own XML browser or interpreter.
The XML specifications specifically define XML to be easy enough for someone to write an XML parser within a week (?) if I remember correctly. It's something farsical like that.
The problem is that an XML document that works fine in one browser is almost guarenteed to fail in a different browser given that XML is an extensible markup language. You are in effect defining/creating your own markup language (eg. HTML is a markup language) and are then required to write a browser or parser for that language you define.
It certainly would be interesting to see this occur in DBP, however I suspect that DB1 would have been capable of doing this task, it just wasn't tapped into.
:: Specs: AMD Athlon XP 1600+ (1.4GHz), 256MB PC133 SDRAM, Leadtek Geforce 2MX SH 64MB, SB-Live!, LG SWrks 775N 17", MS Natural Pro KB, MS Optical Mouse, Windows 2000 Pro (SP3), DirectX 8.1 ::