I'd be devastated if it was a permanent move. I'd love them all to move abroad and live in a different country for a while, as I think it's great for broadening horizons, but I'd really hope that they'd move back to have their kids.
My sis emigrated to NZ as she married a Kiwi; I really miss her and the cousins all miss each other too. We can't afford to go over at the moment, probably not for a long time if I'm honest, and they come over approx once every 4 years. They last came in 2015, hopefully are coming in 2019 but not 100%.
I have come to appreciate my family so much more since I had kids - not just the support, but the interaction between my kids and my family is brilliant to watch. I don't live near my parents, they moved to the other end of the country to be near my other sister, but as they all live in a holiday destination, we go and visit as often as we can.
OH's family is dire and, despite living very close (within 20 minutes drive) we see them maybe a couple of times a year. They are just not interested in maintaining a relationship, although always gush about how lovely it is to see us and how they wish they saw more of us. We've stopped making the effort now - they know where we are
OH's mum lives in another country - I find her incredibly difficult. Luckily she only visits a couple of times a year.
I will encourage my children to live their lives as they want, but I am going to tell them how much I appreciated grandparent support when I had kids, plant the seed early!!!