Regarding new civs, I agree it would be nice to see some new faces, but there's also franchise tradition to consider. I thought I read somewhere that at the time of civ5, there was only one civilization that had appeared in all civ games, the Zulu (although I'm pretty sure America was never absent, same for Rome?). They need to keep that tradition going! Furthermore, the Zulu would accomplish three really cool things. First, the game, as is, has mounted and ranged units as the most flexible and useful, melee land units lack the same degree of utility. Most or all of the Zulu bonuses would probably focus on melee units, which would make them the leading class of units for the Zulu, much as they did in Civ5. Which relates to my second point, that most of the civs that people are drawn to are civs that can utilize strategies that other civs simply can't because of their bonuses. For example, China's wonder spam or better yet, Germanies ICS with triple-district sprawl. Zulu would allow the player to utilize melee unit strategies that simply wouldn't work with other civs. Finally, they'd provide an alternate experience for war mongering. As the game is, Scythia is by far the best choice for warmongering. You could argue that Sumeria is also top tier, but once the era of war carts ends, they still have the levy bonus, provided you can get multiple Suzerain bonuses, but that's pretty much it. The Zulu would provide an alternate experience for highly aggressive players, and could possibly be a civ that almost acts as a counter to Scythia since Scythia's gameplan is almost universally "conquer with mounted units" and the Zulu UU would almost undoubtedly be the impi, an anti-cavalry unit. It would be nice, then, if there was some flaw in the Zulu package that would make them particularly susceptible to a different civilization, which would create a rock-paper-scissors balance among the highly aggressive civs preventing any of them from becoming overpowered.