Well there certainly are tweeters more expensive. Accuton makes ceramic (synthetic sapphire) tweeters costing in the $230-400 range retail. They also make a synthetic diamond tweeter that is almost $3000.
Now do they sound any better? I dunno. But you can spend more on a tweeter than the Scanspeak one that SVS uses.
However for them, the real questions isn't if something more pricey is available, or even if it sounds better, it is a question of if it sounds better enough to justify the price. SVS has made their name as offering extremely good sound for the price. They have never been the "Top dollar, anything goes, audiophile grade," company. Always their products have been good for the dollars.
I can't see that changing with the LTS series, or any new subs. That means that whatever they choose, it'll have to be worth the money in sonic terms. It can't be a case of "This is a tiny bit better if you listen real careful." It needs to be something obviously worth the money.
A big part of the reason for that is because they are Internet only. Many people have a lot of apprehension about buying without hearing, and for good reason (I certainly do). That means when the speakers come in, they need to sound good, to justify their cost. After if they are barely, or not at all, better than what you can get locally, why would you go through the trouble of ordering them?
So who knows precisely what the LTS will be? Currently they are playing with some different designs. Makes sense, as you try some different things, see what works, what gives you the best value for the money.
They could well go with extremely pricey parts like the Accuton drivers, and then maybe you have $10,000-15,000 speakers. They could go with parts that are no different quality wise than the MTS, just a different build, like say a 3-way, mirrored driver tower like the Dunlavy SC-IVs. In that case maybe you have $3,000-5,000 speakers.
You don't necessarily have to buy better drivers to improve sound. The way the speaker is built can have as large an effect. So maybe they decide that the level they are at with the MTS speakers, which is pretty high end, is good enough and they just remove some of the construction constraints.
As for the lack of something like the B4, well I think the real reason is that it isn't as good as two subs. Neat idea and all, but it is entirely possible that 2 PC-13s will give you more bass, and a setup like that unquestionably gives you more flexibility. Doesn't make sense to have a special product if more of your normal products can fill the need at a lesser price.
Goes double now that we are seeing things like Audyssey on multiple sub channels and new formats that may have more discreet LFE channels.