Just some rough calculation:

If AsicMiner can hold about 10% of marketshare (where marketshare = Total Hashpower of Bitcoin network). At this marketrate, it would mine about 131,400 BTC per year (Total amount of BTC mined by network is 25 BTC every 10 minutes -> 1,314,000 BTC/Year).

So for the next four years, weekly dividend would be around 0.00631731 BTC/share or 0,3285 BTC/year/share ( = 131,400 BTC/year / 400,000 shares).

At the current rate of 1.2 BTC per share, this would mean a yearly ROI of 27%. This calculation does not include the amount reserved by AsicMiner to reïnvest in new hardware etc, so ROI would probably be less and also greatly dependent on marketshare.