Scott, basically nobody knows except for Epson. I originally predicted an update for Photokina 2008. Clearly I was wrong. Maybe the next Photokina?
The 3800 is so good that quality-wise the newer printers have only made incremental improvements relative to it. (All of these incremental improvements are very welcome, of course. But they're relatively small compared to, say, the improvements between the UltraChrome K3 printers and the earlier UltraChrome printers.)