Replacing surround with sound bar

The need to simplify is real.  If you aren't a huge movie sound buff by all means switch to a bar.

Personally I have found that taking the time to properly set up a 5.1 system quite satisfying to listen to.

There are a number of eARC to HDMI converters, some very affordable:

https://amzn.to/46Vsz8g

I think I would use surround more if it were provided automatically by the TV.  I haven't used the eARC/HDMI converter enough to know if it transmits surround.  I do use HDMI from the Ayre DX-5 DSD to the Bryston SP3 for Blu-rays.  In my OP I didn't mention that I'd like to end up with the single 4-tier rack of Ayre gear and KEF Reference 1s I have now -- a fine sounding setup, or KEF LS60 with the Ayre DX-5 DSD as the approach to my simplification goal.  In either case, gone are the SP3 and NAD amps.  At 87 I feel the need to downsize and simplify.

I switched to the Sony soundbar added the bigger sub and smaller back channel loudspeakers and have been very happy.  I was using a 2 channel with single subwoofer setup run through a Roksan analog preamp.  I took the analog audio output from the television.  It sounded good.  I then got a bigger, newer TV with very limited analog outputs and thought I should do something.  The sound, particularly dialog, is much better with the Sony soundbar, but the setup and convenience are far, far superior to the previous 2 channel movie playback.  It's all wireless with automatic room optimization and I can use a single remote for all television/streaming viewing.  Unless you're trying for some sort of statement multi-channel viewing experience I would highly recommend the Sony soundbar.

I have not used the Sony for music playback.

The model I got was the HT-A7000.  It's being discounted right now.  Could be a new model coming?

Several years ago I replaced NAD T765 with PSB speakers and Mirage sub for a Bluesound sound bar to down size. 
 

I haven’t regretted it though I use my tv as a monitor for Roon probably more than for tv or movies. 
 

It’s an option and if aligned with your priorities can be worthwhile 

There is a big difference between a real surround system and a soundbar, even a cheap surround system. I would do what you have to do to keep it. I’ll be honest, I’m not sure I understand the eARC issue. The last time I upgraded our TVs… suddenly all the TVs and surround systems and sound bars suddenly started working together under the eARC input. I only had to upgrade my HDMI cable to 2.0 or something like that.

But I understand. My partner is disabled and bedridden, so we have a 65” and a soundbar in the bedroom. I think it is pretty easy to show ~ best is the Sennheiser Ambeo. Add a small sub and you have really good natural sound, but not surround.