Team Changes

So right now I'm on a team where everyone gets along. In fact we get along so well that we'll even get together on the occasional weekend or holiday. In my personal experience and from anecdotes about other people's work experiences this seems to be rather rare, particularly in larger companies with a lot of churn. I really like the group of people I work alongside day after day, but no team lasts forever. People have different priorities and goals and eventually people go their own way. Recently, I have heard murmurings of coworkers considering other options, and while I'm happy for them to be pursuing their own happiness, it's also making me kind of bummed out. I wouldn't say that I love the work I do, to me it's just a job with work that needs to be done everyday. I don't think there's been more than a handful of days where I looked forward to coming to work in order to work on my work. What has kept me eager to come in every day is the fact that I will get to spend time with people that I like being around. My coworkers makes my job fun. This is great but at the same time a bit concerning. I'm not the most outgoing or sociable person so looking out towards the horizon and seeing my work friends leave has me feeling uneasy about my future work satisfaction. I'm curious if anyone else has had experience with this. I feel like this must be a fairly normal part of corporate life, as people change jobs all the time in today's world. Does anyone have any advice on how to handle this inevitable change? Is it worth trying to maintain the social dynamic even after job changes? Should I be trying to make more personal connections that will persist after we no longer with together? Or is it better to approach all collegial relationships as inherently temporary going forward and try and find work happiness elsewhere? Any advice would be appreciated.