I think that would depend on a lot of factors. Some people have more bandwidth for social stuff and can cope with keeping in touch with old friends and also seeking out new ones. Others can't.
But, also, if you are online, you can already know people in the new city. I am somewhat prone to having my friendships start online and then become IRL instead of the other way around. While I am probably not the norm, I am not some bizarre statistical outlier these days either. Plenty of people meet people via Internet and move the relationship to meatspace.
