Shirou probably hasn't got to whatever floor his land is on yet. I'm wondering if by floor 50 (or 75 or whatever) there will be anybody else who gets good enough to earn a title.
From what I understand, Kayaba gives out titles as part of his encouragement to advance the magecraft system. Mainly because, without titles, Cardinal would nerf their (Shirou and Illya's) magecraft to maintain relative balance - and this is something Kayaba doesn't want, as they represent a development of the SAO proto-thaumaturgy engine in the direction of the real world's own principles of magic and magecraft (alchemy, conceptual magecraft and reality marbles).
Essentially, the cardinal auto-balance system, without titles, would work directly against the evolving thaumaturgy-mimicking engine. As Kayaba's goal is not a "fair and balanced game" but instead an accurate model of real-world physics and metaphysics, he hands out titles to players who develop their magecraft in ways that help the metaphysics engine adapt towards its "true" end result, but would result in nerfbatting from Cardinal, or perhaps he would also hand them out where progressing further in a specific field would be unintuitive if not for a title, to encourage a specific field of study.
tl;dr, Kayaba will give titles to those creating [Unique Spells] and making novel developments, as those advance the thaumaturgy engine.
Thus, by my reckoning, the people most likely to receive a title (and thus, those likely to receive a title soon-ish) are, in order: That one dude from LC, Argo and Kirito. There are undoubtedly others who fit the criteria I used better, that I simply can't think of right now, but others might be able to point those out. These people are exploring parts of the thaumaturgy system that others aren't, at least not fully, and thus would seem to be the most likely to acquire a title, based on the fact that they are doing something novel, that advances the metaphysics engine, while perhaps damaging the balance of the game.
First, That One Guy From Laughing Coffin, which I am leaving deliberately non-specific, as it kinda applies to all of them, are very likely to get a title in my mind as they have done three things that we know others haven't, things which could be construed into title-worthy efforts. First, from one of the first LC interludes, we know that Johnny Black was one of the first to experiment on what can and can't be reinforced, creating the [Unique Spell], [Extend Poison] - notably, this is a [Unique Spell], not an [Extra Spell], so at least at that time, he was the only one to have it. Obviously, Johnny, from nearly the very beginning, was experimenting with magecraft in ways that others weren't, ways the system didn't anticipate, which means he might stumble into a title just by advancing his magecraft. Second, we have PoH, who grasped something very, very important - the game's engine respects thaumaturgy. His cursor-colour illusion is a one way ticket to a whole lineage of unique spells that test the engine. The depth of field of explorable paths that you can take once you realise that the game respects thaumaturgy is ridiculous and most likely lead, in part, to LC experiments with summoning. Which constitute my third point - LC made the engine pause, momentarily, through their summoning. This was something that came so far out of left field that the thaumaturgy engine
stalled while it tried to work out a solution. LC is making waves, magecraft-wise, as they are trying new things, hunting for exploits, thinking outside the box and so forth.
Someone from LC is going to come out with a title, just as a matter of time, the question is how long will we have to wait, and how many of their upper leadership will get one.
Candidate number two is Argo, and this is where my arguments get a little shaky - Argo needs different things of magecraft than other players, and unlike many of the other front liners, those needs do not flow in the direction of "moar dps", because, as an info-broker, she has different goals she wants to achieve compared to front-liners players. Furthermore, she has Shirou as an instructor, and has extensive access to the builds and information of other players. If Argo decides that a certain effect would let her get tons of money from her clients, she'll probably try to work it out, with Shirou's help. Argo I think, might receive a title if she takes Shirou's [Nerve Circuit] spell and goes ham with it, progressing further along the [Form Temporary Crest] metamagic path, maybe pioneering her own form of Vancian casting. Alternatively, she might puzzle out divination, and gain access to the "code" of the "world", and start interacting with "the system", or Cardinal!Gaia/Alaya. If we set certain bars (proper divination, understanding circuits, etc.) as title-worthy, many of those are within Argo's reach.
Finally, and least likely for titling, is Kirito - Kirito is creating many unique advancements and playing around with the thaumaturgy system a lot, and would be higher up on this list if not for one reason - he uses Isopsephy, and as Kayaba's own philosophy, Kayaba could just as easily integrate all of of what Kirito has done himself, if he hasn't already. Kirito isn't going to get a title for testing the engine, as Kayaba has certainly already tested the engine's ability to emulate numerological principles extensively - thus Kirito has to go one step further and use them to break the game balance - when Kayaba has likely already anticipated many of the ways it could be done and accounted for them.
EDIT: By the whole "unique developments" logic almost all other members of the BSM are potential title-holders, to one degree or another.