My guess is they'd go into space 133 (see link below), which would allow them outside access... It'd be awesome if they had both entrances open, maybe it'd do something to convince others to switch back. Portage now isn't as bad as it was 5-10 years ago when all the shops closed, and Warehouse One already deals with 2 entrances at their current location.
http://portageplace.mb.ca/directory/
ADD: Also, looking thru the main floor directory, while the stores aren't everyone's cup of tea and none are sure desirable or destination stores — they actually cover the whole range of categories one would expect in a mall, and vacancy is low. Main floor at PP is functioning pretty well and probably accurately represents the makeup of the nearby residents that frequent it the most.