Yes, phone numbers are a legacy of the old telecom systems. SIP uses user@domain style URIs, and this can be mapped to a legacy number via ENUM, and vice versa.

Yes, phone numbers are a legacy of the old telecom systems. SIP uses user@domain style URIs, and this can be mapped to a legacy number via ENUM, and vice versa. 4G cellular networks are all IP and use SIP for signalling. I doubt phones are publicly addresssable though, the telco probably NATs them. I eagerly await a number-free, VoIP-enabled, IPv6 world.