I agree with your statement. However, I think they've already shown their tremendous amount of trust for each other, at least relative to their trust for other nations. Austria-Turkey is usually limited to a few years into the game. On the other hand, it seems like the downfall of Russia took a bit longer, and Austria-Turkey usually falls apart once Russia and Italy are significantly weakened. Turkey will be the one with the larger incentive to stab in any case, since it will take a long time to expand beyond the Mediterranean, but it will be a brutal and exhaustive stab. They may decide to just continue as planned, or batter each other while the rest of the map reorganizes. We shall see.
On multiple players per country: Absolutely, that's why it's so convenient. Far better than watching as countries fall apart because their player was no longer able to play, or forfeit, as I've seen before. Of course, there's the problem of cohesion and contradicting thought from the multiple players, but that makes it more realistic, and seems to have been managed well.