Wow, there's so many comments here I'd like to reference with a quote, but that's too much work.
Primarily, I'd say the most important and surprising thing I've learned about UHD is that its benefits are not anywhere nearly all about resolution vs visual acuity. To a rather huge degree the benefits are also about color space and bit depth. Even at not so huge screen sizes/viewing distances, there will be extremely obvious benefits to UHD content and displays. 10-bit or 12-bit color depth of even Rec. 709 color space would be a vast improvement to 1080p, but I don't think we'll ever see that combo. But UHD specifies Rec. 2020 which is huge by comparison to Rec. 709 and even DCI. The image below shows the comparison on the CIExy1934 pallette. Rec. 2020 uses about 75% of it, DCI a little over 50%, and Rec. 709 only about a third of it. You will be able to see that like night and day! Plus, Rec. 2020 specifies either 10-bit or 12-bit color depth. We're currently watching 8-bit on BD.
You guys might want to go over and look through the thread here on this area about 4K BD coming sooner than we might have thought.
I also think that JVC e-shift2, 3 (whatever) can be a reasonable transitiion projector. It is rumored that the new models will have a 4K/60 Hz input. That must be HDMI 2.0, but we'll have to see. Yes, the JVC will scale it down to 1080p and apply the e-shift utility, but that's not so bad, as someone said. If it can also pass/display the larger color space and bit depth of an input 4K UHD source such as 4K BD, it will indeed be a fine transitions machine. It might even become an entry level "4K" product, with native UHD panels in higher end models.
I'm like some of you; overdue an upgrade, but wanting the best value. I think that the recommendation of the 4810 is great. Even an RS46 with a Lumagen 2021 would be awesome for a long time.
BTW, FWIW, Lumagen will eventually field a product that will accept UHD 2160p24/30 input AND output as soon as the chips to make it possible become available to them. Lumagens already work in the 10-bit/12-bit realm, but we don't really have any content with that depth...yet.