<===Geax is said to be getting their tubeless ready version of the Saguaro tested for UST approval. Look for it to be available soon.
Used to be that when you said "UST" that you were talking about a 26"er tire that you could mount on a UST rim and air up with no sealant. That's it, just like a car tire. Now things are a bit more complicated thanks to the advent of tubeless systems for 29"ers.
At the time of this writing their are no tires that are designed to hold air without sealant or a tube available in 29"er sizes. (Although I have gotten a Bontrager Tubeless Ready Dry X to do just this for a 24 hour period) Why is that? It is because of how a UST tire designed to work without sealant is made.
<===Bontrager Dry X Tubeless Ready Tires sans the AR casing reinforcement weigh below 600 grams a piece. Way below 600 grams!
A tubeless tire designed to work without sealant needs an extra layer of butyl rubber over the inner casing to prevent leakdown after inflation. This adds a lot of weight to a tire. In a 29"er size, a tubeless tire with this extra layer would weigh in at a mark not acceptable to most riders plus it would cost more. This is probably the best reason why you will see the majority, if not all, the 29"er tubeless tires being marketed as "tubeless ready" tires needing sealant to make them work.
Hutchinson was just recently awarded UST status for their tubeless ready concept Python 29"er tire, a tire needing sealant to work. How can it be UST, you ask? Well, many folks may not realize this, but UST has a lot more to do with the standards of rim hook/tire bead interfaces than it does with whether or not you would need sealant to make the tire hold air. Basically it is a standard that indicates the tire with UST approval and a rim with UST approval are safe to use sans tube. How the tire holds air can be accomplished in two ways: with a butyl rubber layer or sealant. Thus you will start seeing Hutchinson Python 29"er tubeless ready tires being marketed as UST.
<==Continental supposedly will release the Mountain King and Mud Queen tires in 29"er sizes in both standard and tubeless ready versions. Hmm......we wonders why, yesss my precious, we wonders!
It would seem to me then that any 29"er tire released from this point on should be tubeless ready. Why not? Get the bead interface to work as a tubeless tire would and use a standard casing. If sealant is used with the proper rim, then you could have a tubeless tire too. Tubed or not tubed, both in one tire. In fact, Geax is pursuing this very thing and calling it "TnT". (Tube no Tube) Brilliant!
I'd go so far as to say that the industry should drop wire beaded tires all together, with the possible exception of OEM tires. Why not? Get all the features anybody could generally want in one format and be done with it. Tires are going to become much more expensive due to high oil prices, so one tire that could go both ways will be seen as a smart buy by consumers too. It won't have to weigh anymore than current tires either. A win/win situation if I ever saw one.
So, look for your tubeless ready tires in 29"er sizes soon. Some will say "UST" and some won't. If you get confused, don't worry, you can always use a tube!