I have no doubt that the PS3 price drop will increase sales, but the question is "will it last?" At the moment, I don't think so. But I could be proven wrong.
As for 3rd parties on Nintendo systems, the problem isn't that they're on a Nintendo system. The problem is that there's really no "compelling" software coming from third parties. They're all pretty much trying to emulate Wii Sports, instead of coming up with their own ideas.
Hell, Dragon Quest Swords supposedly did very well. I think it sold about 300,000 it's first week (not positive), and become the fastest selling console DQ spin-off. Resident Evil 4 sold 150,000 in it's first 10 days.
It's going to be unique, interesting software that sells on the Wii. Spin-offs, etc, won't always cut it. I get the feeling that RE:UC and Soulcalibur Legends won't do so well due to being (seemingly) rushed out.