2G will be live until atleast 2025. Longer term, my guess is it will ultimately be shutdown. You should get some life out of 2G kit for a while yet, but it would be prudent to have an upgrade path in mind for the future.
Vodafone plans to shut down 2G networks in 2025. I don't think 3G is going to be shut down in New Zealand anytime soon. Vodafone 3G won't go until at least 2035 I think. When 5G becomes standard (around 2025ish) other providers may think about shutting down 3G - not until at least 2030. Rural areas still rely on 3G these days.
Other countries are planning to shut down 3G and some already have.
