My buddy is thinking of upgrading to this TV https://www.sony.ie/electronics/televisions/af8-series

It costs around €2500 and it's pretty high end. 4k oled amongst other features. I was talking to him about HDMI 2.1 and I don't think these sets support hdmi 2.1. I'm not an expert on it but is hdmi 2.1 likely to be important on the ps5 and next gen in general. He games on the ps4 Pro but his next console will be the ps5. Should he hold out a few years for a 2.1 capable TV? 

Not knowing the specs of the PS5, it's still very likely that Sony will support VRR (Variable Refresh Rate) on their next gen console. Afaik the Xbox One X already does that. That would be the main reason so far, to go for HDMI 2.1. 

It will support HDMI 2.0 which means it supports 4K@60fps.

Thats all you will need for next gen. Consoles will never push for more that 60fps in the living room.

Truth be told is that chances are most next gen games will be running at 30FPS in 4k ain t how we have most running at 1080p@30fps this gen.

Or they run with dynamic 35 - 50 fps when stable 60 fps ain't possible on a HDMI2.1 TV with FreeSync 2... which would be much smoother than your suggested 30 fps.

I wouldn't invest in any display without adaptive sync technology at this point.

Hmm, this one is tricky since at 4K HDR10 at 60fps HDMI 2.0 is enough as we see with PS4. However when support for eARC will probably be there on PS5 (for Dolby Atmos passthrough for example.) It's an HDMI 2.1 standard but a lot of TV's already support it without having 2.0 for example the Sony AF9.

I guess it's best to wait for CES in 2 weeks and see what Sony will release on their next gen TV's.

But only in YUV 4:2:0. YUV 4:4:4 or RGB 4:4:4 is not possible for 4K 60fps HDR10 due to bandwidth limitations on HDMI 2.0.  

HDMI 2.0 should be fine for next gen gaming.

HDMI sucks with it's non forward compatible protocols. I still have a HDMI 1.4 receiver so am limited to using ARC for 5.1 compressed sound while enjoying 4K HDR. Upgrading to a HDMI 2.0 receiver is pointless at this point with HDMI 2.1 currently phasing in. HMDI 2.1 tvs are coming as well. Besides that HDR is still an evolving format, who knows what it will settle on. HDR 10 will be replaced.

So the Sony AF9 doesn't support 2.0 let alone 2.1? I know it has eArk but assumed it had 2.1.

Another thing I read was that LG have a monopoly on the production of OLED displays making it likely the price of non LG sets won't drop in price much over the next few years. 

So Xbox X has 2.1 but not full 2.1 support. 8 presume the ps5 and next xbox will have full support. 

The next TV purchase I make which I'd be aiming for March 2021 is important to me. I'd like to think the TV will not only be perfect for PS5 but also PS6 which will likely be a 4k 60fps standard machine that features some games at 120 fps 4k. It's not guaranteed but I'd consider it a fantastic purchase if I could buy a tv in 2021 that will satisfy me for 2 full gens. That's my goal. Maximum value for money.

I read this comment on YouTube. Anyone any thoughts?

"HDMI 2.1 will be such a gamechanger because TVs will finally be on par with PC monitors input lag. Makes me glad I returned the cheap crappy budget vizio 4k i bought in 2015 and spent a little bit more and got a nice 1080p Sony Bravia to hold me over. Hopefully HDR 10+ will be cheaper as well, when I finally get my 5 year future proof TV when the new sets roll out next year I want 1080/1440p@ 120hz, 4k HDR 10+, HDMI 2.1, and FreeSync. Now that would be my dream TV heading into 7nm age! I just hope I can get one for like 1000 and no more, will most likely be between NU9000 series or X900G if sony and samsung stick with the model name scheme."