If Paradox can do it, then I think Firaxis can as well - and all their grand strategy titles now come on Mac simultaneously with the PC release (not to mention, companies such as Blizzard and Maxis have been doing that for years, but I think Paradox is a better comparison in terms of sales).
Blizzard have ceased Mac development of all new titles, including Overwatch, because they consider Apple's graphics support and hardware insufficient. The big game companies aren't going to take Mac gaming seriously until Apple does.
As for Civ6, the current line-up of Macs are going to struggle to run it. Many struggle to run Civ5. Despite the less 'realistic' graphics in Civ6 (which I really like), they'll definitely be more resource intensive than Civ5. More animation, for a start.
I think the view that Mac OS sales are not worth a dual platform release is frankly speaking quite outdated. A lot of gamers now have Macs (and use consoles for more action-based games, such as Witcher 3) and especially when it comes to games for more mature players, it is a vibrant market.
I agree, but it's a perception that's hard to shake. What is making a difference though, is iOS gaming. That's a huge market, and once a game is ported to iOS, it's not too much of a leap to get it running on the Mac as well. This has led to a lot of big titles, albeit a few years old, coming to both platforms. What we need is the reverse situation: developers doing dual platform releases of their new games, knowing there's further money to be made down the line with an iOS port. Again, this relies on Apple committing to proper graphics support.
As long as the mod doesn't change the dll of course, but that's to be expected I think.
The DLL is what I'm referring to. With Civ4 and Civ5, Aspyr deliberately folded the DLL into the application itself. If they hadn't done this, we could have figured out a way to take a mod's source code and compile it for Mac. I contacted Aspyr about this prior to Civ5's launch but they flat out refused to consider doing it differently, stating that they had no obligation or interest in supporting modding. This was their attitude for Civ4 too, shipping it with Python 2.3 despite the Windows version launching with Python 2.4. Refusing to fix Mac-specific bugs and memory leaks that you only noticed if the game was modded. And the only reason we even had a game editor in Civ3 is because one of their (now former) employees, Brad Oliver, put it together in his spare time.
As a Mac modder, I'll be very disappointed if it's Aspyr doing the port again.