The worms will probably not wander out into the rest of the bed. Composting worms are littler dwelling worms, not soil dwelling worms. However, the roots of plants in the raised bed may migrate into the worm bin. I have piled up finished compost on a tarp on the ground prior to using it. When I finally got to it, it was choked with roots from the neighbor's lilacs on the other side of the fence. They grew right through the tarp. When the finished VC in the bin gets deep enough, you may find the same thing happening in your worm bin.

Delightful and inventive.

Very nice concept. It is great to have castings near the point of use.
If you add lots of compost, some worms may wander for a bit. After both worm and raised beds are established, the worms should stay with their food.
Roots will enter the bin. I have lots of cypress tree roots sucking the goodness out of a pile of castings I have neglected ( the trees are quite healthy though!). This may be what you want. I have sifted out roots and returned them to the bed.
You may consider adding a removable or hinged "trap door" along the bottom wall of your worm bin end. This would facilitate easy removal of castings without disturbing the run.
Good luck and keep us posted.

I think the worm bin should run along the raised bed so that the castings will be close to the roots of each plant. The design above will benefit the plants closest to the bin disproportionately.