I wouldn't say that they've already been superceded as this platform is targeted at a different market segment. I may have misunderstood what you meant but it's almost like saying there isn't much point in AMD releasing the HD 4670 when the HD 4850/4870 are already out.
DDR3 prices are dropping rather nicely and many of the features of Bloomfield LGA1366 removed, motherboard costs should be far more reasonable too, so Core i5 shouldn't be terribly expensive either.
Upgrading to Core i5? This may or may not be worth it but I'm not willing to write the platform off from a couple of meanlingless SuperPi 1M times. The CPU could really shine in multicore apps, in the same way that i7 does. Then there's how well they overclock and how performance scales with higher frequencies. Finally, there's price. This will make or break it as it'll have to be significantly cheaper than going i7 and will have to be priced aggressively against AMD's Socket AM3 offerings.