Will x1900 push cards prices lower?
Formal price drops are unlikely. The X1300s are going to remain stable and the X1600s already had a large price drop. As for the older generation, the X300, X600, and X700 are already very low, and since they are on clearance I doubt ATI provides much guidance on the anymore. The X850s, X800XL, and X800XT will likely receive price drops not from ATI MSRPs but simply because they will no longer be supported. It's unlikely ATI will formally lower the prices of the XL, and XT types much to prevent tarnishing the image and target market those names are associated with. The last of the R4xx inventory will be cleared through the GT, GTO, and GTO2 brands. Those prices are likewise already bottomed out. Any lower and they would infringe too much on the X1600 which isn't what ATI wants.
Now pricing of the X1800 is an interesting matter. The X1900s are supposed to be direct replacements for the X1800s which are going to be discontinued. This is still contradictory since manufacturer websites like HIS Digital seem to indicate that the X1800 will remain to fill the gap between the X1600 and X1900. What's even more interesting is that if the X1800s are truly discontinued there is a very large gab in ATI's modern product line. The X1900XTX replaces the X1800XT OC at $649, the X1900XT replaces the X1800XT at $549, but there isn't anything to replace the X1800XL. Most likely a 512MB X1900XL will be released soon priced at $399 and a 256MB X1900XL at $349, with the higher X1900s falling $50 to close the gap. The huge gap between the $179 X1600 and the current $300 range X1800XL will likely be filled with X1800GT and X1800GTO parts allowing them to clear R520 inventory.
ATI is also working on two new mid range parts. With only 4 actual pipelines, the X1600s haven't been that impressive being remeniscent of the X600. Luckily they have high clock speeds. The RV530 is going to be replaced by a 80nm die shrink RV535 which will lower costs while allowing for further clock speed increases. The RV560 is also in the works and is a complete redesign of the RV530 and will be named the X1700. Most likely the RV535 will be named the X1650 and be a direct line replacement for the X1600, while the RV560 X1700 will fit into the $150-$250 market.
With ATI finally regaining the performance lead, they don't have as much need to aggressively price their components. This will change quickly in March when the 7900, 7600, and the 7200 is released. ATI will likewise refresh their product line at that time, which is when the RV535, RV560, and the low-end RV505 will be released. Prices will drop aggressively at that time. Sorry for my tangent, but I kind of returned to the topic by the end.