Some things worth noting:
1) Reaper has an ability called Arcane Crest which is functionally similar to TBN.
Arcane Crest: Absorb incoming damage up to 10% of maximum HP. Duration 5 s, recast 30 s. If shield is nullified, all party members within 15 yalms gain Activated Crest (Restore target's HP every time they attack; 100 healing potency, Duration 15 seconds). If even a DPS job has something like this, it's not a stretch to see what direction they're going to be taking tanks.
2) "Upcoming Adjustments: Tank
Using defensive enhancements at optimal times will grant greater benefits."
2) While TBN was shown in the job action preview and seems to have the same duration, we didn't see it being used on another player.
3) The new bubble action can be used on both yourself (Endwalker Benchmark) and another player (job action preview).
4) PLD and WAR both have new self defensive buffs that could functionally occupy a similar space to TBN.

I suspect that we're going to see a few things here. TBN will probably replace Dark Mind as your low level defensive and probably be self-only without a cost. It'll probably have some sort of a buff tied in to breaking the bubble. TBN 2 will probably take over TBN's old role as a resource based defensive that gives you DA procs to stay DPS neutral. The fact that it has a 10 second duration attached means that it probably will be an weaker bubble than the original.

The one interesting thing about tying bubble breaks to dps and even utility buffs is that it devalues invulns. Your bubble is either redundant or it doesn't activate if you invuln it. This is the part of the live letter which both worried and intrigued me the most.