Thanks again to all. I guess my most important takeaway is that it is best to chose a device where the manufacturer has a track record and process for firmware upgrades, where possible. Best way to protect the massive financial investment (I use that word loosely) that the industry requires.

Ok, I think I've got it. The Oppo non-All-region, connected directly to my LG TV, and my a/v receiver plugged into the Oppo HDMI input.

Problems solved:
- Oppo HDMI input will scale anything coming thru my a/v receiver to 4K
- Oppo will play any current and forthcoming UHD / HDR Blu-Ray format and all audio modes
- All-region support from my iVid, which works well for me, is retained. I will not be purchasing 4K materal outside of my region, so the Oppo is overkill for the all-region feature. The iVid plays Blu-Ray and all DVDs very well.
- Oppo direct access to my data servers will allow playback of native 4K content
- 4K Apps (VUDU, YouTiube, Netflix and Amazon) from the LG TV, or 4K media player.
- If I need more 4K inputs I will put a switcher in front of the Oppo input later
- least cost immediate purchase with maximum impact. I can schedule the purchase of other components when / if I have the funds, and meanwhile the excellent Oppo firmware upgrade policy helps protect me from the industry movements. I might be able to get Oppo into the budget next month. 

Anybody see any holes in my plan?

Yes, thanks mostly to you and the others who responded. Saved me lots of grief and possibility of wasting money. I can do without the dual HDMI until I upgrade my projector - way down the road. Then I'll just use the best HDMI 4K splitter available at that time. Thanks again to all!!

It depends how capable your current receiver is. Does it support ARC and 3D?

If you connect your receiver to the Oppo's HDMI input, I don't think 3D is an issue, as the Oppo can transmit a 3D video signal directly to your TV. The Oppo itself can play 3D blu-rays and 3D files.

You may want to think, however, about how to feed your receiver with audio from the Oppo. If you use the Oppo's HDMI audio-only out, you would in fact be creating a HDMI loop with audio signals going both in and out of the Oppo. I'm not sure that will work, but you can try.
What you can do is to use the Oppo's analog outs and connect those to your receiver to transmit your Oppo's sound to the receiver, I reckon. You would lose Dolby Atmos and DTS-X, but not hi-def audio.
Audio from the TV - e.g. the Netflix app on the TV - can go into your receiver using either ARC or an optical cable - at present ARC does not support hi-def audio anyway, so you lose nothing by going optical. (I use it myself to get TV sound into my receiver).

Quoting dee1959jay:

Quote:
If you connect your receiver to the Oppo's HDMI input, I don't think 3D is an issue, as the Oppo can transmit a 3D video signal directly to your TV. The Oppo itself can play 3D blu-rays and 3D files.

You may want to think, however, about how to feed your receiver with audio from the Oppo. If you use the Oppo's HDMI audio-only out, you would in fact be creating a HDMI loop with audio signals going both in and out of the Oppo. I'm not sure that will work, but you can try.
What you can do is to use the Oppo's analog outs and connect those to your receiver to transmit your Oppo's sound to the receiver, I reckon. You would lose Dolby Atmos and DTS-X, but not hi-def audio.
Audio from the TV - e.g. the Netflix app on the TV - can go into your receiver using either ARC or an optical cable - at present ARC does not support hi-def audio anyway, so you lose nothing by going optical. (I use it myself to get TV sound into my receiver).

Since all of my inputs go into the receiver, the audio will come out as normal, when the receiver is on. When the receiver is off, I get the last selected input via the pass-thru feature, and I turn the TV volume up. The only time I need the audio from the Oppo is when I am playing directly from it. In that case, I just use my existing optical out from the LG, with the receiver switched to the Tape input, where I have assigned the optical input channel. The HDMI audio out or optical from the Oppo are other options that I will play with - again, only needed when the Oppo itself is the source and I want the receiver sound. Otherwise, everything coming from or thru the Oppo plays via the TV sound, which is actually not bad for casual listening.

Thanks for double-checking my plan, but I think I'm ok ... 

Oops, never mind the original post. Analog would work fine. Lots of flexibility on the Onkyo.

FYI: the first Dolby Vision HDR UHD discs have been announced.