No, INTRODUCED in 2007. Sheesh.
The web page on Sony's site says "No longer available.". Retailers may still have stock on hand, but once that's gone, the D50 is history. A 4.5 year lifespan is pretty good in the fast-paced world of consumer electronics.
I think there are three factors. First, the M10 is superior in several ways, which likely reduced sales of the D50. Second, in the D50's price range, the competition has added multi-track recording and XLR inputs. Third, the D50 uses Sony's proprietary Memory Stick flash memory cards, which are hella expensive in large capacity and hard to find. The SDHC and SDXC cards are the way to go today.
The Roland R-26 is the best example. Quiet preamps, 6 channel recording, price $499.