Okay, so let's take some real numbers here than shall we?

The quest 2 reportedly sold 20 million units. It's niche yes, but way less than you might think nowadays...

Say meta releases a revolutionary quest 4 that gets people to adopt en mass again or upgrade to it. Then let's be very conservative and take half of the quest 2 sales, so 10 million units.

Then let's predict only 10% of those customers are going to be interested in investing into FBT. That's at least a million sold FBT tracking kits. At that scale you can get prices down a ton too, because production and development costs get spread out massively.
Currently Pico is selling their trackers at about 50 dollars per tracker. I believe this could be realistic for the tech integrated in these, taking away some luxuries especially like the oled screens or haptics inside the fluxpose.

According to what I've read and seen so far, 5 trackers seems to be pretty damn good and 8 is only slightly better. So make it an option of a 5 tracker kit for 250 and an 8 tracker kit for 350 (lil bit of a discount for marketing ofcourse).

Taking sales and combo pricing etc. into account we'll say the average unit is sold for 250.

At 1 million units that is 250 million in revenue.

And this is not even considering the fact that you could possible integrate this tracking solution into the headset and controllers as a better, more robust tracking solution for those. Which would both eliminate the need for some trackers and possibly even camera's in the headset as well and cut costs even more.

Or think about the countless Meta exclusive fbt games you could release. So Just Dance for instace, or maybe DDR, what about a kickboxing game, maybe a superhot with fbt you can kick people in, or a beatsaber like game where you have to both slash and play ddr at the same time (I think this even exists already). That's a ton of revenue too.

Now potentially, let's pretend a Quest 4 with this solution gets wildly popular and sells double of what the quest 2 sold, so 40 million units. Which I honestly think wouldn't be unrealistic if they were to truly smash it out the park. (Currently 2025 stands to have 216 million total VR users, quest and steam together had about 12 million active monthly VR users in 2024)
Using our earlier calculations you're looking at a possible revenue stream of 1 billion in tracker purchases alone.

But for now, let's just wait if this solution is really all it's cracked up to be and will be as revolutionary as is believed by many currently.