San Diego has definitely become a resort destination, like Hawaii, and I think this could keep the rents and the home prices high for many years to come. We in uncharted waters, with SD just finishing its first housing boom in the internet age. The internet fueled the boom by giving people easy access to information about the SD housing market and making it logistically easier for people to move on out here.
San Diego certainly is more attractive than NYC and the other big cities you mentioned on price/sq.ft. basis. But those other cities are more costly due to the fact that they are much bigger and have many more cultural offerings than SD.
What makes me scratch my head is the market in San Francisco. That city is not too much bigger than SD, and the weather is much worse than ours. Why are the same houses selling for 30-40% more money up there? I have friends who just moved into a house for 1.2Mil, but that same house would only get around 700-800k in San Diego. Maybe if we can understand what makes the prices so much higher in San Francicso, we can understand what might be the key to (eventual) higher prices here in SD.
