The Airport operating area is between Matheson and 407. Development is allowed as long as it is not residential. There are some high-rise office buildings already.
So at least high density is possible there, unlike between QEW and Port Credit GO, because of the rich NIMBYs. I don't think much much will happen north of SHopper's World either, outside of Downtown Brampton.
Dundas-Hurontario is low income now, but with all-day GO and LRT on Hurontario and maybe even Dundas too? Who knows. That area actually has the highest developement potential of all the Hurontario corridor....
In my experience, Hurontario and a few other routes like Burnhamthorpe and Dundas have huge crowds while the rest are empty due to low frequencies. The GO train is a joke but ridership would go up by an order of magnitude if service was improved. The 21 and 45/46/47 GO buses are busy though.
I don't know when you use the bus or which buses you're talking about, but living here I can say Mississauga buses are usually at least half full, even during midday, no matter the frequencies (and they aren't that bad). Rush hour, the buses are usually standing room only. Hurontario is a busy route but it doesn't exist in isolation. People transfer to/from other routes.
The MT routes with highest weekday boardings as of 2012 are as follows:
19/103 Hurontario/Express - 27,802
1/101/201 Dundas/Express - 19,998
7/34/35/87 Airport/Credit Valley/Eglinton - 14,135
26/76 Burnhamthorpe - 11,448
3 Bloor - 8,040
110 University Express - 8,034
5 Dixie - 7,170
42 Derry - 5,913
13/29 Glen Erin/Park Royal - 5,805
61 Mavis - 4,864
22 Finch - 4,572
66 McLaughlin - 4,474
23 Lakeshore - 4,139
http://dmg.utoronto.ca/pdf/tts/2011/validation2011.pdf
Note that the numbers for Hurontario don't include 502 Zum Main or 2 Main, which saw 9,244 and 2,720 boardings per weekday in 2012. It's possible some of these people transfer to MT 19/103 so there's some double count, but I think it's safe to the Hurontario-Main corridor currently sees over 35,000 riders per weekday. That's at least 10 million boardings annually. Factoring increased mode share, development, people going out their way to use the line, anyone still think the LRT cannot reach 29 million?