No it wont because it does waht it says on the tin, which is loop.

If you want to mirror and watch it do its thing. Simply go to duplicate Special under edit then select 1st half of the model, then in the scale attribute box simply type in -1 in the x or z channel, this will depend on the direction you have modelled.
Then click the 'instance' geometry type radio button and hit apply. This will then flip you model allowing you to model on one half and watch it update on the other half. When you have done, simply combine the mesh and merge the verts

Jay