Hope, not supported and I would not even try it. Even multi-location businesses that are managed as individual listings done in the dashboard are not supposed to merge with Google+ yet.
See point 2, section 2 here. That advice still stands. In fact with the roll out of the new Places dashboard, Google is still recommending even individual listings not merge yet until they get the new dash with the new G+ widget.
Plus my 2 cents is that merging one location is buggy enough as it is. I think it would be self inflicted torture to try to do it for many locations.
No, Google does not give timelines or projections.
My assumption is, it's all hands on deck - working on finishing the new dashboard and getting merge problems ironed out for the 2 most common scenarios; single location storefronts and service area businesses.
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