It would also be difficult leaving immediate family left here on the East Coast, but with one sister and three nieces already spread across the U.S., I've had years to cope with that reality. Now, with fewer years in front of me than behind, it's unsettling to envision day-to-day life without regular interaction with my newest tribe.
Would I make new friends? Of course. How? Likely via some of the same techniques used when I moved here sixteen years ago. I'd join - or start - a book group or two. I'd volunteer, get involved with a local activist group, find people who enjoy hiking or being outdoors. My wife would try to connect with folks who love gardening and I'd try to locate musicians and other aspiring writers. One of the upsides to the Internet is how easy it can be now to connect with people that have similar interests. And staying in touch is also much easier than it used to be.
But, however, still ...