It's a straight shot down Sheppard, but what if it were to turn down to STC? Ending at McCowan is still kind of a subway to nowhere.
It is a subway to nowhere. Sure some buses will move to Sheppard, but the GO Bus, and Intercity buses along with the proposed BRT to Durham are still all going to be at STC. On top of that you still have the fact STC is also planed to have a massive amount of development both residential and office, alongside the large commercial space in the mall itself. I cannot undertsand how some people believe having the sheppard subway skip STC is a good idea. The sheppard subway going to STC has been on the books since Network 2011; why? Because it's the correct thing to do. We have been talking about the idea of "Sub-Centres" in Toronto since the 70's and STC has been the sub-centre for Scarborough since then and that is not changing.
As for moving bus routes, looking at the TTC map today the only routes I see logically stopping at Sheppard would be the 129 McCowan North, 130 Middlefield, 131 Nugget, 169 Huntingwood, and the 85 Sheppard, (and maybe the 16 McCowan if they want to run a parallel bus service to fill the gap. They could also just extend the 129 south to STC). So 4 or 5 of the 13 or so buses that stop at STC. STC will still be the main bus terminal for scarborough.
Comparatively buses stopping at STC to me at least would be: 9 Bellamy, 16 McCowan, 21 Brimley, 38 Highland Creek, 43B Kennedy, 132 Milner, 133 Neilson, 134 Progress, 178 Brimorton (assuming it becomes a permanent route), and the 903 Kennedy-Scarborough Centre Express. As well as the aforementioned connections to GO, Intercity, and possible Durham buses.