The question isn't if it is a bubble - it is more if the factors driving the bubble are likely to change - that certainly does not seem to be the case.

Government policy appears to be hands off beyond new tax rackets.
Immigration is full steam ahead.
World is as unstable as ever and foreign money wants to come more than ever.
Regulations continue to cripple new development.

Nothing will change until it is a crisis and that will probably need another year or two of 25%+ gains.