San Diego has been called the City of Neighborhoods. As a practicing architect in San Diego, I look @ the future of these neighborhoods from a modern urban planning perspective.
Which is San Diego's next up-and-comming neighborhood? Where should you buy property? Where should you build your dream home? Which neighborhood is right for you? Read on to see the results of this analysis.
Buy land. They're not making it anymore!
-Mark Twain
Let's not tip toe around it, San Diego is super expensive right now. So the development I'm recommending is a long-term investment. This speculation considers the next 1-3 decades of ongoing development, including additional density radiating from the downtown core of the City (which I believe is inevitable). There are so many variables to this equation, but for the purpose of discussion I'd like to focus on the most basic given concepts: (1) buildable land, (2) property value, + (3) easy access to obtain a regulatory approval for development. The comparison of these specific components of development is a very architectural way of looking @ the future of San Diego.

A 1-mile, 2-mile, + 3-mile diameter from the center of Downtown San Diego. As population increases, some urban sprawl is inevitable.
One of the 1st things that has to be understood when considering a property for development is the location. This should be done both on a macro-scale + a micro-scale.
Topography is easy to overlook on a flat map but could mean the difference of a hip, walkable community. San Diego has plenty of natural land formations like canyons + cliffs which divide neighborhoods from each other. Highways also divide the city in a more manmade way. These obstructions can allow pedestrian passage w/ a bridge / tunnel, overpass / underpass.

The waterfront, Balboa Park, + the San Diego Airport are permanent obstructions to development. These will funnel future development North or East + South East.
Major boundaries would be the San Diego Bay, Balboa Park, + the San Diego Airport. All of these are important / historical to the region + will be preserved into the future. Downtown San Diego cannot expand into these areas -it has to expand to the adjacent neighborhoods to the North + to the East to Southeast.
Little Italy (to the North)
Bankers Hill (to the North)
Golden Hill (to the East / Southeast)
Sherman Heights (to the East / Southeast)
Grant Hill (to the East / Southeast)
Logan Heights (to the East / Southeast)
Barrio Logan (to the East / Southeast)
Once these neighborhoods gain density the next set of neighborhoods could begin to densify (South Park, North Park, Hillcrest, + Mission Hills).
After location, the next thing reasonable person would be concerned w/ is the cost. When comparing the mean listing price (info provided by Trulia.com) it's obvious that property value increases North towards La Jolla. Conversely, the lowest property value is to the East + Southeast.

Home values (green / yellow / orange / red, lowest to highest) throughout the region increase to the North / West, while decreasing to the East / Southeast.
There is another component which is often overlooked by home buyers looking to develop their properties, the dreaded Coastal Zone (generally everything West of Route 5). Projects in this area require a complicated Coastal Development Permit which requires applicants to submit additional documentation + make presentations to the community. These permits cost thousands of dollars more + can be held up for years -all w/o a guaranteed outcome. Most developers prefer to mitigate their risk (the tighter the budget, the better to avoid this risk).

The California Coastal Zone (shown blacked out) creates permitting challenges, increasing cost, time, + risk for developers.
This narrows the selection down to these 'entry-level' neighborhoods:
Golden Hill (to the East / Southeast)
Sherman Heights (to the East / Southeast)
Grant Hill (to the East / Southeast)
Logan Heights (to the East / Southeast)

Because of the central location of Balboa Park, as population increases downtown has to expand in one of these 2 directions: to the North or to the East / Southeast which is about twice the size.
Property buyers will have to make a binary decision; expensive development or less expensive development.
The entire analysis in a single Gif
The opportunity is ripe for young home buyers to scoop up some of the most affordable homes in San Diego + then build a 2nd one behind it. Developers will likely target the larger industrial properties in Barrio Logan or along Commercial St. for neighbored mixed-use developments.
If you have any questions about this information, or would like to set up a consultation for architectural design of a property in these neighborhoods please reach out.