That is the thing ... as far as i know Larian never explicitly confrimmed that they will not implement anything from other sourcebooks ... there was some hints, but nothing too specific so that we can base some assumptions on that.
On the contrary they repeatly told us that they are looking at other books for inspiration.
Also both whole Ranger and Dragon-Sorcerer are certainly alterned by other sources ...
And as we say in my country: Hope dies last. :P
As far as players handbook stuff, Larian has explicitly said that they're aiming to get everything from the players handbook into the game, but I highly doubt they're restricting themselves to that. The sense I get is that players handbook content is where they want their floor to be, and they're prioritizing getting all that in but if they can get other stuff in as well, they will. I doubt we'll see other classes or races outside of PHB, but at least a handful of other subclasses seems like it would be doable.
Huuuh, fair enough. Here's to hope then! \o/
