By significant, I mean sustained improvements. If all you manage is a spike in sales, it doesn't amount to much in the long run. In fact I think you've acknowledged as much in the PS3 price drop discussions!
If each 'Japanese' titles nets MS an extra 1000 a week sustained, it's not going to win them the market or a significant share. Likewise spikes in sales aren't going to accumulate into significant numbers unless there are lots of them. BD and TB haven't fired up the market, so I don't see what more MS can do in that respect, short of buying SE and making FF and DQ XB360 exclusive!