I've also read reports here and elsewhere that some Poly guests are being offered to switch to GF due to overbooking.
Steve's speculation seems to be the most logical reason why this is happening (especially given that they never did the scheduled room refurb in Tahiti in combination with the recent South Florida Water Mgmt permits).
This also suggests to me that Disney is really gearing up to pull the trigger on all of the refurbs (e.g., GCH, Nanea pool) and not just the ones directly related to DVC construction because it makes the most sense to do these (i.e., live with less demand) when the resort is not at full booking capacity.
In addition, it tells me that they are serious about trying to finish by late 2015 or early 2016 beause they won't want these units sitting idle for any longer than necessary. Along those lines, I would think they'd want all of the other resort refurbs (GCH, pool) to be done by the time they open DVC and since they're likely to do these in stages, they'll want to start sooner than later.
As of just a few days ago, I was (wishfully) speculating that the Nanea pool and GCH refurbs wouldn't happen for at least a year because Disney has a track record of dragging their feet on projects, especially since the GF DVC isn't quite finished (so why hurry on Poly DVC?). Moreover, if the Nanea pool were to be closed for, say, 7-8 months as was the GF courtyard pool, it would seem to make more sense to close it over the fall-winter (as they did with GF courtyard pool) than from January through the busiest part of the summer.
But with Tahiti and possibly Rapa Nui down, having the Nanea pool down over the summer is less of a concern because, as noted above, Disney can live with less resort demand.
If I had to wager a guess at this point, I'd say there's a pretty good chance the Nanea pool will be down for the better part of 2014 beginning in January and that work on removing the GCH main water feature may likely happen at around that time as well. Then, once the work to the pool and water feature is done, they'll work on the parts of the GCH that involve (at least temporarily) closing shops and restaurants.
So overall, I'm guessing Nanea pool and GCH water feature construction through the better part of 2014 and various GCH restaurant and shop closures through the better part of 2015.
In view of all that, I still can't decide whether to cancel my May 2014 reservation.