One thing that I heard a bit ago, and when I think about it it makes a lot of sense, is actually ending the DRL at Barber Greene, with the south end overlapping the rail corridor. Hopefully by the time the DRL is built there is some sort of GO service running on the Midtown line, in which case having a DRL transfer point there would take a lot of pressure off of Summerhill Stn for downtown-bound passengers, and by extension the Yonge line southbound. It's not a significantly further distance than Eglinton, and would provide a lot of added benefits.
As for Don Mills north of Eglinton though, I think the best bet for the foreseeable future is a dedicated lane BRT service (I know, surprise coming from me). The service could run from the terminus of the DRL all the way up to Unionville and Downtown Markham, hitting Fairview and Seneca along the way. It would go a long way to funnelling eastern York Region riders off the Yonge line, especially if the BRT service featured some kind of a semi-express service once it reached Seneca.
Until that BRT, which would cost almost nothing to build, because Don Mills already has HOV lanes, is bursting at the seams like the Broadway BRT in Vancouver is, I don't think a subway further north than Eglinton would really be warranted. But I think spending a few million on a BRT service on that corridor and then having it be a tremendous success in need of upgrade is a much better approach than spending billions on a subway extension and having it be a flop. At least if the BRT service is bursting at the seams you know a subway along the corridor is viable. And as it stands today, I'm not sure that a subway north of Eglinton is.
As for Don Mills north of Eglinton though, I think the best bet for the foreseeable future is a dedicated lane BRT service (I know, surprise coming from me). The service could run from the terminus of the DRL all the way up to Unionville and Downtown Markham, hitting Fairview and Seneca along the way. It would go a long way to funnelling eastern York Region riders off the Yonge line, especially if the BRT service featured some kind of a semi-express service once it reached Seneca.
Until that BRT, which would cost almost nothing to build, because Don Mills already has HOV lanes, is bursting at the seams like the Broadway BRT in Vancouver is, I don't think a subway further north than Eglinton would really be warranted. But I think spending a few million on a BRT service on that corridor and then having it be a tremendous success in need of upgrade is a much better approach than spending billions on a subway extension and having it be a flop. At least if the BRT service is bursting at the seams you know a subway along the corridor is viable. And as it stands today, I'm not sure that a subway north of Eglinton is.