Some HDMI 1.4 receivers have 4K passthrough for unprotected 4K content, but you will have to throw them away as soon as HDCP 2.2 protected content is available, or you'll have to use a source with dual HDMI out, one for the AVR for sound and one direct to the display for video, like some HDMI 1.4 do for HDMI 1.3 AVR which can't passthrough 3D.
Buying an AVR today is madness unless you know it won't be in the video path.
This applies to switches, VPs, etc of course. The whole video chain will have to support HDMI 2.0 and HDCP 2.2 or 4K protected content will not play.
And I just bought my AVR... in fact, bought 2 of them..
I guess we're caught in the middle of the 4K madness.
I am going to venture another out of this world prediction. Since the trend is now towards downloading / streaming content, the upgrade path may be shortened.. ie, we might see 8K being rolled out just when 4K's standards are finalized... so, we might be in for a long ride of having to change equipments...