IQ is still better than what you can buy with similar money ; no question about that.
Advances in the cameras/sensors on the Sony side have been much more about AF, technology like IBIS, etc...
And lens advances since have mostly done nothing in terms of improving IQ. Many of the very best lens in the world from any brand are much older than the RX1
The RX1 real value is the amazing and tiny lens attached. The value of the Rx1 will remain fairly close to current used pricing, as the lens itself is worth roughly that. The body that is attached will for the most part be devalued at next to nothing but the lens is still worth a good amount of money, is the Loxia 35 lens any better and what is the cost of that?
So to answer your question, if IQ is your main criteria than the Rx1 original is every bit as good now as when first introduced, if you are more concerned with the latest technology and best AF then you could be disappointed in buying this model vs the newest model (say Sony 6300 and a separate lens).
In general I think the camera best fits one of two buyers:
1.) the experienced user that has decided they can cope with 35mm as a sole focal length, they may have experienced back issues or similar mobility concerns or event that has caused them to rethink their camera goals but still demands highest IQ
2.) the user that also owns an ILC but sees the value in buying a second body with the 35mm lens rather than a separate 35mm lens to use on their existing body. Gives them a backup option in case anything happens with their other body, will be more portable, no worries about changing lens in wet/dusty environment and cost is really no different.
If you don't fall into one of those categories the Rx1 may not be a good fit, IMO.
online gallery at:
www.MattReynoldsPhotography.com