It is a little early to determine driver support for D:OS 2, since platform support has yet to be announced, besides Windows. When that decision is made, if applicable, presumably the popularity and stability, etc, of the mesa drivers at the time would influence whether support would be added.

From the Kickstarter FAQ:
Quote
Right now, we're focusing on Windows only. Additional platforms may be announced in the future.

Believe us, it's not that we're not interested in producing a version for Mac/Linux/Console, it's just that we want to get the gameplay and world fleshed out in all the detail that it needs first. Once we have the game fully worked out, we'll start looking at porting it to other platforms. That’s not something that’ll happen during the Kickstarter or indeed this year.

But - and it’s an important but - we do have most things in place to support several other platforms, since we are starting work from the Divinity: Original Sin- Enhanced Edition engine. We just don’t want to make any promises yet.