The built-in threat meter that Bornakk hinted at yesterday has made its way to the latest build of the Wrath Beta. Tipsters John and Hugimbory point out that the Beta now shows the percentage of threat on the target, updating as it changes relative to other attackers. MMO Champion also reports that the % of threat is shown on the scrolling combat text based on the party or raid member with the highest threat. Mob tooltips also show threat percentage, all indicating simple data forwarded to the client.
WoW Insider reported Nethaera saying that built-in threat meters were coming "in a future patch" back in February. It now appears that the 'future patch' she referred to will probably be Patch 3.0. It remains to be seen whether this implementation of threat monitoring will stay in the game as is, although it's more than likely that the system will still receive some polish.