If you go by "skate to where the puck is going to be", the puck, when it comes to communication, always moves towards platform agnostic protocols. (.. and Skype provided a decent fraction of Facetime's functionality well before Facetime).
If the likelihood of a person using platform A is P(A), then the likelihood of two of them communicating is of the order of P(A)^2. So even if you have 20% platform penetration, that only gives you a communication likelihood of 4%, leaving plenty of space for other providers to fill.
If the likelihood of a person using platform A is P(A), then the likelihood of two of them communicating is of the order of P(A)^2. So even if you have 20% platform penetration, that only gives you a communication likelihood of 4%, leaving plenty of space for other providers to fill.