It absolutely doesn't depend.
The ridership numbers, current and future, are far less east of Kennedy Station than they are to the west. Ergo, the headways will be quite a bit different - and thus may not blend well. As well, where are those people from the east of Eglinton heading to? Probably two-thirds are currently heading down the B-D - assuming that that ratio stays fairly similar to that in the future, they won't benefit from a through-running line in any case. And finally, longer transit lines have more problems with headway adherence - so why make the line any longer than you have to when the benefits are so minimal?
.