Will old saves be affected when the new update goes live?

Yes, but only...

I say only...

There may be the super small kinks.

Mods, for one, will break until mod developers can catch back up and update the mods to be compatible for 1.2.

So if you use mods, be prepared for that.

But also, again, there might be some, just with every game ever, when you jump from patch to patch, there's just gonna be a small little few, like, quirks here and there, unloosening, revealing their buggy colors.

But if you are on 1.1 still right now, and you are using vehicles in your saves,

Do be prepared for the roads of those vehicles, the paths of those vehicles, I should say.

Be prepared for the paths of those vehicles to be treated as legacy paths by the game from now on.

And you will be strongly encouraged to get rid of every old path that you have going and make new ones instead.

So there will be some manual labor for you to do redo with your vehicles, but it should be much quicker and smoother and honestly very fun to set up.

So there is that.

So yeah.