The article doesn't suggest that Bhutan has a future in the leadership of Tibetan Buddhism, but that when/if Tibetan Buddhism gets more fractured because of disputes around lineage, then Bhutan can become globally important in the thought leadership of Buddhism more generally, or maybe more specifically Vajrayana Buddhism.
Do you have a link to the Karmapa admitting he's not the real deal? I tried to google it but got nothing.
There is this: https://youtu.be/AdI4DMRFkm4
Although here he admits "he is not properly trained as previous Karmapas" that's not exactly the statement i claimed
There was also another one with a stronger statement, somewhere during covid, I need to dig more
There are 4 main schools of Vajrayana Buddhism: Nyingma, Kagyu, Sakya and Gelug, and the Dalai Lama is head of just one of them - Gelug. They have independent teaching transmissions and succession lines. There's common misconception about Dalai Lama being a kind of a "pope" for Buddhism at all, or for the Diamond way (that means Vajrayana) Buddhism in particular, which is simply not true.
Having said that, it is of course unfortunate that the issue with two candidates, one of them "manufactured" by the PRC regime, is on the horizon and most likely will happen. Please note this already happened for the Kagyu lineage, where two Karmapa candidates emerged in 90s; interesting that after few decades the Chinese one admitted recently he's not the real one.