As much as I would love to see a Traditional Linux (TL) tablet from a productivity standpoint, I don't think it's necessary.
The structure of the FS, traditional applications, a rich scripting environment, a modifiable kernel through modules, regular multi-tasking, etc, etc, etc.
Rather than start from the beginning, why not extend Android? It already has mass distribution, and implementations on swaths of product.
At its core, Android runs a stripped linux kernel and standard libraries -- It's essentially linux, with some different software than is found in traditional distributions and a unique FS structure. It would be FAR more prudent, to create a bridge between the two OSs and fill in the feature gaps missing from Android, rather than start from scratch and hope for traction.
And please don't say that it's not possible. It has already been done with VNC and chroot.
A deeper integration may take creativity, but I assure you, if you can shoehorn Windows apps into Linux, you can certainly do the same with TL apps in Android.
On the flipside, it would be great to give Android to TL in the same way that Android has been integrated into RIM's QNX platform. Imagine having access to the Android market on your Ubuntu distribution? Certain apps/games would be quite welcome. I would use it tomorrow, given the opportunity.
It's all open source.
I don't believe that this Android vs. Linux needs to exist. I believe that they can quite literally coexist at the same time, on the same hardware, and much more quickly than trying to develop a mobile linux variant from the ground up and hoping that somebody will notice in this hugely competitive marketplace.