I would categorize the gentrification areas as being 1. gentrifying rapidly where the neighbourhood is currently under massive transformation, 2. gentrification started, where some gentrification is starting to happen and 3. pre-gentrification, neighbourhoods which haven't yet been noticed for their full potential as gentrification candidates but have all the hallmarks of a potentially great neighbourhoods.
1. Gentrifying Rapidly: Leslieville, Upper Beach, Parkdale/Queen West West, Dundas West of Bathurst
2. Gentrification Started: Junction, East York, Mimico/Lakeshore Village, St Clair West of Bathurst, Riverside/Rivertown, Queensway
3. Pre-Gentrification: Upper Junction, Danforth east east, Weston Village, Mount Dennis, Scarborough Junction, St Clair West West, Gerrard East/Chinatown East
In the downtown core, its inevitable we will see many more high rises and that will appeal to the young urban crowd. But when they decided to have families, they will likely move into one of the above neighbourhoods or the already established hoods like the Annex, Riverdale, Bloor West Village, Roncy etc.
From both an investor and end-user perspective, you have to be able to view gentrification as something that will now start ot occur more beyond the DVP--Davenport--Dufferin--LakeOntario perimeter. This perimeter is already saturated and well under way to be high-rise city in the next 10-15 yrs because of the cost of land and construction, it will leave developers no choice but to build as high as possible to maximize returns within that perimeter.
The neighbourhoods outside this perimeter are the ones that hold a lot of promise and the lower cost of land will allow for savvy developers to create livable buildings (read: The Hive and some StreetcarDev projects).