Yeah, you're right. There are a lot of fans who wanted to know more about him (myself included). He was one of the characters that I loved to hate. As little screen time as he got, he was still the next baddest of the bad guys when I was growing up. There was Vader, and there was Fett. And they were badass!
Rogue One brought the Bad Ass™ back to Vader (after many long, agonizing years of not-so-bad-assy-ness) and I wouldn't mind at all seeing Fett in a similar manner.
And if that happens to drive
The Mandalorian forward, then so be it. But, if he shows up in TROS I'm not gonna be happy about it.