10 is already announced for smartphones via a streaming partnership with NTT Docomo.Any reason given for stopping before IX? It would be awesome to have an excuse for a revival of that game someday. Amazing game, not that I wanted every DQ to be like it.
Hell, given how quickly mobile hardware is improving, we could see X soon enough.
http://www.neogaf.com/forum/showthread.php?t=688051