Ok, I'm psyched for this. Lots o' thoughts and I'm not fully caught up on this thread yet, so apologies if I cover something already discussed to death.
Anna Nzinga: Oh me of my this is awesome news. Absolutely no clue how they'll implement her as a leader, since 1.) Kongo's CUA is really strong, and only really balanced by Mvemba's malus against religious victory. Maybe since it's so late in the game cycle they don't care about Civs getting pushed, though, and 2.) Anna's historical role was rooted in her diplomatic strengths. There's potential for that to translate into game mechanics, of course, but how that will synergize with the CUA will be interesting to see.
Lincoln: Another one that's tough to predict based on what he's famous for. (I suspect this is why we haven't gotten him since they moved from Leader Traits to LUAs, honestly.) If I wanted to wildly speculate, I'd guess they'll use the "Team of Rivals" aspect which has become noted in recent years (thanks to the Doris Kearns Goodwin book of the same name, obvs) and do something with Governors/Governor Promotions. Which could make for a very powerful, and flexible, ability if that's the route they decide to take.
Ramesses II: Cool cool cool. I'm on the "pro-Cleopatra" side of things, honestly, though I understand folks not being wild about Egypt currently only being represented by a Ptolemy. Ramesses seems like he'd probably be a builder/conqueror? Hard for me to guess how they'd make that fresh, but a new Egyptian option will be good to have. I still like Cleo though.
Elizabeth I: Honestly, if we're getting another English ruler just give us Liz Truss so I can player her on Marathon speed, please? I kid, I kid. Elizabeth is one of those rulers who can pretty much go in any direction they feel would make England more interesting. Imperialism? Check. Religion? Check. Diplomacy? Check. Trade? MAY I INETEREST YOU- ahem, check. Culture? Obviously check. So really I have no idea here.
As for this Leader Pass pushing back Civ VII, I'd take it more as a sign that Civ VII is taking longer than expected, and that being the case, here are some ideas to tide us over. There are worse things on earth, honestly.
As for other leaders I'd like to see, or at least would find interesting:
Germany: I'd really love to see a Peacecraft-focused Germany, since there are at least a couple of notable examples from history and it's a more interesting and, well, positive aspect to celebrate than the warcraft side, in my opinion. We're not going to get Angela Merkel before some hypothetical Civ XII 50 years from now, which means Bismarck. Bonuses for those "makeshift alliances" perhaps?
Arabia: Harun al-Rashid most likely. One of the Rashidun could be cool but possibly thorny with Shi'a Muslims (I might be off-base about that, though.) Saladin's ability is very interesting and the civ well-designed but I think there are a lot of different ways that one could go here.
Scotland: Mary Stuart, a.k.a. Mary, Queen of Scots. Not the most effective ruler historically, but a fascinating figure (in keeping with the "Big Personalities" maxim for Civ 6 rulers) and there could be an interesting mechanic in Religion/Loyalty akin to Eleanor's culture/loyalty ability.
Willem van Oranje: I like Wilhelmina's inclusion in the game but any alternative to Radio Oranje as an ability would be welcome.
And, of course, Japan, Spain, and Rome could all have fun with new leaders. Russia too but it's hard to feel too excited about playing Russia these days.