Telegram doesn't store your messages forever and they are encrypted and seizing the servers won't allow you to decrypt them unless you also seize the correct servers from another country
> This could be extremely useful for security. Maybe even the death of VPNs.
You can already get plans from the existing cellular providers to drop you onto a private secure network that behaves like a VPN though... that's common for people who need secure OOB access to their network gear: but install routers with 3g/4g/LTE expansion cards, get the SIMs on one of these plans, and voila -- OOB remote network access that isn't exposing your devices to the internet
Telegram doesn't store your messages forever and they are encrypted and seizing the servers won't allow you to decrypt them unless you also seize the correct servers from another country