Depends. If you were to punch something through to 10 dundas somehow from the redevelopment to the south of the SLC it would likely come out somewhere around where the Shoppers in 10 Dundas is today. It is possible, but you would lose retail space in 10 Dundas.
There will likely never be a connection to the SLC however (and therefor a connection to Ryerson's small indoor network, unfortunate), as the ground floor of the SLC is rather unfriendly to a connection.
The second entrance to Dundas will likely come in the base of the redevelopment to the south of the SLC, and will only be from the northbound platform from its absolute north end.
Am I the only one that feels like Ryerson has been missing the chance for additional connections to its indoor network? currently only 3 buildings (SLC will be the 4th) are connected, but the engineering building, image arts building, and student union building all could have been easily connected through underground tunnels.