In the next few years I might want to move to a new city with my wife. However there are two problems here: 1) I have developed a pretty decent social network here in my current city and I don't want to lose it. 2) The only social network I have in the new city is my family and a couple of college friends.
In the time I have to prepare, how should I best extend my current social network to the new city while shoring up the current network so that I the loss is minimized? Extra information that is helpful here is that I'm a software consultant, so good portions (but not all) of my current network are comfortable with dealing with me remotely. And also because I'm a software consultant I currently have the ability to travel before I permanently relocate.
Note: I've answered similar questions in the past, but this is different because I hope to leverage my current social network to extend to the new city.
Networking Geography Social Network
It can work if you put in the time to keep in touch with your old network and build a new one when you get here. Get yourself out there - meaning, network and find organizations of relevance to you - when you do get to NYC. The beauty of this era of social networking is that you'll maintain contact with existing contacts while creating new ones.
By "extending" your current social network do you mean "continue to maintain those relationships both personal and professional?" While physically moving is disruptive, it's not like the pre-social networking days where you had to expend a lot more effort keeping in touch with individuals, peacemeal. I'm based in NYC and I have contacts I've met overseas working with our EU partners that I speak with more often than some old friends in the tri-state area.
On the professional front, if you're a software engineer in NYC there are countless meetups and other local activities to get in on. Try leveraging your university alumni network as well, if possible.
But you have to put yourself out there, and don't be reticent about sharing your status and talking about what you're up to to keep your 'old' network alive.
One idea that comes in my mind, is that you slowly start transforming your communication channels from meeting in person to remote communication that you will be able to use in future.
However psychology of relationships and networking suggests that you keep someone within your network only if you have some sort of benefits from him/her. So for example, if you have a buddy who you mostly do sports with and occationaly go for a drink after, then most likely you won't keep him in your network, because there will be no more benefits from him. And in that case you shouldn't feel too bad as you will always be able to get a new buddy after you move.
So given the fact, that every person has limits on number of people he can stay in personal contact with, you should aim to keep most relevant contacts from old place, those that can't be easily replaced. I know it might sound cruel, but I've had similar experience and I remember I was thinking exactly the same way you do now, but still that was the best conclusion I could possibly get to.
I was mainly regarding to non-professional contacts. With proffesionals from your field of expertise, in my opinion, staying in touch shouldn't be something to worry about.