Ah what a good rumor – so much so I hope its true. Psynister Notebook is blogging that their will be new heirloom rings and legs added as part of the Darkmoon Fair. He has already written a comprehensive guide to heirloom items, and with these our alts and twinks should be even better geared. Or is that overgeared?
New Rings and Legs for 1-85 are most welcome. I couldn’t see the declaration specifically in the Wowhead post he’s referenced, but there are links to Rings and Legs within Wowhead, so it is not beyond the call at all (eg. New Tanking Legs). Far more likely than the next expansion being based upon Pandas at the very least.
Do we have enough Heirloom gear now though?
A typical character can be outfitted already in a brutally powerful set of items, to the point where they are typically well above the power of a character not using them. Now I don’t have an issue with this at all, but wonder if the plan is to eventually give us a full Heirloom set that is a matched style and function. Boots, bracers, added in, and then revise (or upgrade / trade-in) the older heirlooms to function from 1 to Max level.
I’d personally love to see it, and think that the slow addition of extra gear is another way we’re being encouraged to stay in the game. It is not a bad strategy – don’t over nurf the content or XP too much, but instead offer players a tool to accelerate through the content should they choose to. No free levels, but certainly fast levels.
It just remains to question what the currency for the heirlooms will be. I hope it stays as Justice points, but could see those pesky darkmoon tokens being used too.
I’ll be reading the patch notes specifically for that now.
TyphoonAndrew's - Eye of the Storm 
As I mentioned in the post, the DMF update mentions heirlooms but it doesn’t actually say which heirlooms they’re talking about. It could be the new heirlooms that were datamined back in December (legs and rings), it could be something completely different, or it could be the very same ones we have right now. We just don’t know.
As for what the currency for them will be, I’d actually be surprised if it’s not DMF tokens. I have a feeling that DMF is supposed to become the Cataclysm version of the Argent Tournament, where players can go to pass the time and earn some additional rewards. That’s also why I still question which heirlooms they’re really talking about when they mentioned it. Is it going to be these new heirlooms, or are we just going to get yet another time sink grind that gives us another route to purchasing them? Hopefully we have the answer to that soon.
I’d like to see full heirlooms implemented, and I think adding them in two slots at a time is a decent pace to do so. We still need Shield, Bracers, Gloves, Boots, Belt, Neck, Wand, and Relic (shirt and tabard not included). I’d also love to see them add in literal heirloom enchants that would also increase in power as you leveled up. Enchants aren’t necessary by any means, it’s just another thing I’d like to see them add in for us.