As for Zellers locations likely becoming Targets, I'd go with:
Toronto:
Warden/Eglinton
Cloverdale
Shoppers World Danforth
York Gate
Woodbine
Centerpointe [sic]
GTA West:
Burlington Mall
Trinity Common
Shoppers World
Bramalea City Centre
Square One
Erin Mills
Sheridan
GTA North:
Hillcrest
Bayview/Wellington (Aurora)
Upper Canada Mall
GTA East:
Pickering Town Centre
Ajax (Salem/Hwy 2)
Oshawa Centre
Brooklin
In the maybe column:
Lawrence Square (one might see this mall redeveloped with the Lawrence Heights project making it a useful property)
Dupont-Dufferin Galleria (with site development)
Gerrard Square (not large enough, but would be good location with reno/expansion)
Bridletowne (Would need lots of attention, but a decent location)
Malvern Town Centre
Thorncliffe Park
Cedarbrae
Milton Mall (with redevelopment)
Unsuitable:
Brampton Centennial Mall
Queensway-Kipling
Westdale
North York Sheridan
Georgetown Marketplace (small store, in same plaza as Wal-Mart)
Bolton
Orangeville (Orangeville Mall)
Davis/Leslie (Newmarket)
Taunton/Ritson
Unserved markets:
Markham
Vaughan
When Wal-Mart took over the Woolco stores, there were a lot of underserved markets. Wal-Mart refused outright some stores like the one in Barrie which was a small downtown store. Others were replaced very quickly when it found a partner in First Pro (now "SmartCentres"). Brampton had no Woolco, so the first brand new Wal-Mart spec store was in Brampton. I expect Target to have a similar relationship with RioCan, and RioCan is slightly better than SmartCentres - it also operates traditional malls unlike SC.
(If it is ever built, I could expect the Osmington mall in Brampton to score Target - half the appeal of the Osmington mall is to serve under-retailed Georgetown and area)
It is interesting to note that in Woolco, Wal-Mart quickly gained two-floor stores in malls, which it was never used to. I never expect Wal-Mart to open in a new mall (like the one planned for Northwest Brampton), but it hasn't been quick to be rid of its mall stores - I can only think of a few stinkers like Blandford Square in Woodstock and Morningside Mall that it dumped quickly.
When it built a new store at New Sudbury (the main mall in the region) to replace the old small Woolco store, the new store remained attached to the mall.
RioCan's Stockyards development would be a perfect site for a Target, likely making a Dupont Galleria Zellers site moot.