The majority of the low-density parts of Etobicoke and North York have to take the bus to the subway. This whole "transit equity" argument falls apart quickly. Scarborough isn't being hard-done by anyone but the politicians lying to the people about the subway.
People aren't complaining about having to take a bus to the subway, they're complaining about the lack of access to the subway in their areas. Just count the number of stations (SRT doesn't count) and you'll see the difference.
North York has 20 stations and has a population of 672K
York has 4 stations (+6 from the Crosstown & Eglinton West) and a population of 145K
East York has 3 stations (+3 from the crosstown) an has a population of 118K
Etobicoke has 4 stations (+ 6 potential grade-separated stations from the Eglinton West LRT, + Humber College)) and has a population of 365K
Scarborough has 3 stations (+3 potential stops from the SSE) and has a population of 632K
It's quite easy to see the discrepancy.
Scarborough is a much larger suburb, and Toronto as a whole has an underdeveloped network. If we as a region got our act together and built the relief line up to Sheppard and Don Mills, much of Scarborough would have a much shorter bus ride to the subway.
No, it won't, it will decrease
subway commute times for the majority of riders, and will make trips far more reliable. It'll definitely decrease the ride for the few people that don't take Line 4, Line 2, or won't use the crosstown to ride west to Yonge (maybe 20K people), but it certainly won't benefit the majority of Scarborough bus riders, who generally live east of McCowan, or within 2 km west of a proposed SSE.
The DRL largely serves to reduce North York/East York/York Region bus commuters overcrowding on the Yonge line, East Old Toronto bus commuters using the Bloor Danforth Line, and Scarborough subway riders on Line 2. It's nowhere close enough to Scarborough to benefit a significant portion of bus users.
I concede that Scarborough Town Centre is an important node and the question of how to connect it to the greater network remains an important question. I personally think Eglinton should have been branched at Kennedy and tunneled through the Golden Mile, but that has not been on the table for a long time. (Or is it, if Doug keeps delaying the Scarborough projects? ?)
Personally, if we want to do something with Eglinton, I think that once the Relief Line North is built, we should cut Line 5 short to Science Centre, (assume the western extension is built as a grade-separated line), and run that line like a subway line (High frequencies and whatnot without turnarounds). For the eastern section, rebrand the surface section as a new line and include the Eglinton East extension to UTSC. The line is too long and has two very different operational patterns. The majority of people using the eastern section want to get around Scarborough, East York, or get downtown, so there's really no need to interline it with the western crosstown at Science Centre Station.