It's not out of the question, however there are many obstacles to overcome, such as licensing, validation, and the fact that the OSM community generally insists on manually entered data.

I've heard many folks push for consolidation of various open data projects, so they aren't "competing" for contributions. However the reality is that they are currently very different and each serves to bridge a very specific gap.

In the meantime, it makes a lot of sense for projects relying on open data to pull all of these sources in, as Mapzen Search is doing, to ensure the best possible coverage.

That's the wrong question - the question is wether the sources from OpenAddresses can be merged into OSM. I know of at least Denmark that there was some address import.