Currently you can enable tabs or a pager, not both.
A pager applies to all the posts on a page (imagine it without tabs). So you could have, say 20 posts on a page and then have a pager at the bottom to show the next 20. On the first page say 10 of them are post type A, 8 are post type B, and 2 are post type C. But on the second page of 20 all 20 of the posts are post type C.
Now you add tabs by post type and you expect that when you click the tab for post type C to see 20 posts for C and then a pager to see the next 2 posts. In reality you get to see 2 posts in that tab and a pager, and on the second page you see 20 posts in that tab.
Tabs by post type takes the existing page and consolidates it into tabs but only for the current page. Thus a pager won't work the way you expect it to work.
Why not just increase the number of posts per page when enabling tabs?
In the new Template and Layout panel whenever you enable tabs the number of posts to show is set to the maximum (and the control disabled). In this situation you won't see a pager unless you have more than the maximum number of posts per page (192, I think). Does this not solve the problem? Is there a need to have pagers when using tabs?
You can increase the number of posts per pager but the pages can get very long and if it hits a pager it still doesn't behave like a user would think it works. I tried explaining the problem above but maybe I need to dink around in a sandbox to show you.
Here's a crazy idea, we ditch the pager altogether, replacing it with an AJAX loading More link/button thingy that's smart enough to take into account the tabs by whatever functionality.
Now that sounds snazzy! I like it. Pagers are so old school anyways :)