Bitmain have never said that it will be possible to upgrade the S1 so not sure why so many people think it will be.

It's still unknown what the upgrade path will be for S2's but it's likely to be just replacement blades, and it remains to be seen how good a deal it will be.

You won't be able to swap 10 blades with the ones from the S3 as the power consumption will be too high, so it's either going to be different blades with underclocked chips or fewer blades say 4 to match the 1000w PSU.