Heh. I just made another comment saying that Tether is not like Madoff, so of course I now need to make one comparing Tether to Madoff.
Bernard L. Madoff Investment Securities was also registered and regulated, and also had to wire people their money when asked. Even though they didn't actually have all the assets they said they did. He was able to keep it up for 3 or 4 decades.
It will only collapse if outflows exceed inflows for long enough to deplete their supply of assets. Which is something that is unlikely to happen for as long as this Bitcoin rocket keeps racing toward the moon.