Are phone numbers obsolete?

Last week my iPhone had issues. It would not recognise the SIM card. With no Mobile Data I relied on WiFi. The experience made me wonder

When will phone numbers become irrelevant?

With so many connection points, Facebook, Email, Twitter, Skype, Facetime, iMessage I was never unreachable, didn't miss any calls and achieved all my communication and social engagement needs.

Landlines are all but antiques these days and unified communications tools are developing fast. 

Your email address or even simply your name could be enough to find points of contact.

Phone numbers often change, with jobs, locations or other reasons. Your email, name, Facebook or other social media profile are less likely too.