I only view a potential cheaper slimline PS3 for the future as more of a direct competitor to the Nintendo Wii (at least untill its release IMO Sony should keep the PS2 well supported).
At this point I think PS3 vs 360 is more relevant, EA expects the PS3 and 360 to go head to head for the United States (personally I expect a significant victory for christmas 2008 even for in the US, UK and Australia) and they think the PS3 will beat the 360 significantly for Europe (with which I agree).
IMO for Japan, the PS3 will crush 360 sales this year. I don't think anyone will dispute that, especailly considering the high profile exclusives and multi-platform 360/PS3 games significantly pushing more PS3 hardware than 360 hardware.