To my knowledge T-Mobile, the last remaining 2G/GSM provider in the US, is pulling the plug December 31, 2020. AT&T and Verizon shut theirs down several years ago and the coverage area from T-Mobile has been getting smaller for a while. This is nothing new.
Yes, to switch to 4G requires new hardware. The 4G module we are using is the Digi Xbee3 LTE-M module – which is both more expensive and more finicky than the 2G unit. I’ve never seen any bulk discounts offered on the Digi website or through any of their suppliers. We’ve been buying them in small batches as we need them. They’re usually in stock through a number of US suppliers. We’ve toyed with the idea of developing our own LTE board, but we haven’t pursued it.
As for selling the 2G unit – if you can find a buyer, that’s certainly better than trashing them. The death of 2G is imminent in the US (and I think Canada) but it’s not gone globally.