If you want to know when x265 is going to be in a usable state you will have to ask the developers about that. Though I'm pretty sure they don't know either.
If you want to know when h265/HEVC will be starting to get actually used I'd say earliest end of 2014 though more realistically in mid 2015.
Why? At the moment the devices most profiting from this new codec are mobile handsets that operate on limited data plans and 4K TVs.
As Smart TVs often use the same SoCs as smartphones and tablets both will happen pretty much at the same time.
Qualcomm already released a preview of its Snapdragon 805 which will be a SoC with h265 hardware decoding support. Thats the most important step towards the widespread adoption of a new codec, without hardware support most smartphones will have a hard time with playing back h265 content. SoCs that also support hardware encoding will come out in 2015 (f.e. Snapdragon 810). At that point all important factors on the consumer sides are ready for a widespread adoption. Now we just need to wait until even the low-end SoCs have hardware playback support.
Though that might go faster than expected with ARM v8 being around the corner at the same time. There might be some more rapid changes again in the Smartphone market.
Something like Handbrake will come around pretty quickly, its not all to hard. In the end its just a good user interface and some good presets. You just have to come up with it.