You seem to be grossly underestimating how many people play games like Civ in MP, particularly considering that what you want here appears to be something entirely unrelated to what the game actually is.

Yes I never try modern civ MP, I discover that simultaneous system recently and read some articles about that (http://forums.2kgames.com/showthread.php?92881-The-Civ-5-Multiplayer-Paradox http://forums.civfanatics.com/showthread.php?t=450433 ...)

maybe... all the people I know don't play civ MP (that maybe the reason why I don't...) we are probably not representative 

when you search "civ 5 multiplayer" on google the first line of the first link says : "Civilization 5 can be fun to play multiplayer. However, there are some 'quirks' that can make things frustrating or difficult" (http://civilization.wikia.com/wiki/Civilization_5_Multiplayer_Tips)

when you search "civ 5 multiplayer simultaneous turn" > most of the links are explanation of how does it works (the first link explain that it's bad)

That demonstrate that is not intuitive 

I still think it's very strange to make simultaneous turn (conceptually speaking) because turns are specially design not to be simultaneous. So when you make simultaneous turns it's not intuitive and they are issues

Ok the game is historically turn base so all GC3 will be TBS including MP, I understand that...

But you don't find that simultaneous turn reinvent the real time?

is there any advantage of simultaneous turn over real time for MP except that GC is historically a TBS?

From now GC is just solo but in some times it will be also multiplayer with probably simultaneous turn, which is a kind of real time no?

Simultaneous turns are problematic if you're playing competitively, because you get into click races when there's a thing that two people are both one turn away from. Most of the time they work fine though, and in coop they're great because they really speed things up.

Endless Space uses simultaneous turns to great effect (shame it doesn't have allied victory though).

There's issues doing sequential turns as well: namely that if you go beyond two players, everybody spends most of their time waiting.

No, because they're still turns. If I spend 15 seconds moving ships on my turn and you spend five minutes doing planetary management on yours, then I just have to wait for my next turn. The turn doesn't progress until everyone's done, so people still get whatever time they need to think, plan, or get distracted by children. The faster player doesn't typically have an advantage over the slower one just by virtue of speed, which in a realtime game they absolutely do.

If the single player game is turn based, then the multiplayer game has to be turn based as well otherwise you have to write what is essentially a different game. So yes, the big advantage of simultaneous turns is that it lets MP sitll be turn based, but workable with more than two players.

I prefer PvP over PvE...

Yes but if there is no time limit there could be a lot of waiting time and if there is a timer you don't have all the time you need and if you have a lot of planets/ fleets you won't be able to do all what you want. So yes the influence of speed is decreased but not totally. In Sin of a solar empire, with a very well though interface / game system you managed all your empire in real time very quickly winning was no a question of speed, So there is way to resolve that in real time too: with a great game design.

If the time is too limited for your empire size you should be more hurry than in a real time game

It could be the day after tomorrow then... 

sequential turns are too long and you can't play with/against a lot of players   

Tomorrow never comes ..... fortunately.

Brad has stated very firmly it will not be RTS, ever. I cannot see how that's not clear, or even start to believe its an unambiguous statement.

Let alone the fact that he has put countless hundreds of hours of personal time building the best TBS AI in the Industry - like he really is going to dump that and re-write for a RTS game ..... its just not happening.

Stardock have approached the whole issue sensibly. As a Company they have their feet firmly in TBS and RTS Stables. When you make a game from ground up, it matters little at Company level which you go for (just don't change stables halfway). Stardock have in the last few years made strides in the RTS world, tine now to get on with an acknowledged success story GalCiv TBS, quite apart from Brad's personal effort invested in the Game as Majority Shareholder.

Its been a dead topic for years, Stardock will not move on this, GalCiv staying TBS - end of story.

The only way that will change is if you want to buy him out for $50million or so. However I honestly don't think even that temptation will change his mind. He may not be in the top ten personal fortune brigade, but he's well enough set for life to carry on doing what he loves doing - and at present that's keep GalCiv as TBS, and no amount of yelling from avid RTS fans will change that, they tried and failed since the early rushes of GalCiv2.

Rock solid Sales figures from the GalCiv TBC Stable mean he will keep going down that road. There are no Shareholder pressures for maximising revenue (one of Stardock great strengths), all that's in the Frame is his personal Driver.

The only time he will change is when it starts making a loss .... and for the moment, that's not happening anytime soon.

Stardock knows, but they're keeping it under wraps for now.  I'm really looking forward to what they have in mind on several of these fronts.  Comparing the real thing to all of our speculation will be fairly humbling, I'd bet.