This
CBC article talks a little about which company could fill the space left by Target. It specifically suggests Wal-Mart and Loblaws (Superstore) are thought to be especially interested as it would limit potential for a new competitor to enter the market.
In terms of Winnipeg, only Southdale would seem to have a strong Wal-Mart potential. The other three locations are too close to existing stores even if they were bringing something like the Neighborhood concept to Canada. Polo Park is a possibility but would need to replace the Empress store and there is likely little advantage to the move.
Loblaws though struck me as definitely being an interesting opportunity. For most people Loblaws in Winnipeg is Superstore. A few more will think of it as Extra Foods and perhaps even the No Frills we will soon see here. Their recently acquired Shoppers brand is also likely not a player in these leases. What is potentially interesting though is the smaller brands they have to play with, specifically T&T and the currently mothballed Nutshell concept. T&T is an Asian grocery store similar to Lucky's which was announced as a tenant for Polo North (where Marshalls is located). Nutshell is basically Loblaws take on a Whole Foods style of store that they were preparing to pilot however they cancelled those plans before the first store opened.
If Loblaws used multiple banners they definitely could be a player. For example Extra Foods or No Frills in Southdale, T&T at Polo Park and perhaps Nutshell at Kildonan Place. Grant Park of course gets the short end there again but it is unlikely that there will be a 100% fit regardless of who takes over the leases.