Phasing out and no stock is 2 different things.
The reason why you can't find 290 is because last month they launch the 290 promo at $499. Some brands like sapphire sold at even lower pricing.
The reason is for clearing stocks on their r9 290. AmD news mentioned that they over manufacture since launch due to cards being snapped out for bitcoin mining.
Other than that yes 290 is a hot selling card. 290x to reduce the price will see how it goes. Cause now the price gap after promo is very big. $499 vs $799.