I agree with your post I think we will see United resume as much TATL as the can, and we will see United try some new stuff (case and point IAD-ATH is working out really well for UA this year as is ORD-KEF).
Do you have data or insight on IAD-ATH? Would be keen to know how that's doing.
AA is allegedly doing extremely well on ORD-ATH so it might indeed make sense for UA to give it a shot.
United has never publicly put out data for a any specific routes and believe it or not I don't have access to that internal data especially if you are talking about yield or the profitability of a specific route in this case IAD-ATH or ORD-KEF. All I can say is what United states which is all they ever state which is the route is exceeding expectations.
I haven't heard anything on how EWR-DBV is performing but I have heard IAD-ACC is performing well and this December and part of January United will increase frequency for the holidays and they are looking at increasing frequency in 2022 from 3x weekly to 5x weekly. EWR-JNB is another route United has remains silent on for the time being and for now there the US still has a travel ban banning nonessential travel from South Africa which continues to impact South African's trying to come to the US. However US citizens can travel freely to/from South Africa.
When it comes to United and routes the only information they will every release is this: A) The route is exceeding expectation, B) The route is meeting expectations, or C) The route failed to meet expectations. United will never give out more information than that publicly, and like I said I don't have access to any specific data as it pertains to specific routes.
With that being said I do think come spring/summer of 2022 if the US has dropped its travel ban effecting European citizens and if Europe is totally reopened to fully vaccinated Americans I think there will be demand on both sides of the Atlantic for leisure travel and we might see United perhaps add some leisure destinations like ORD-ATH or ORD-BCN to chase some leisure fares. If demand is strong enough leisure fares to/from Europe next year probably won't be cheap not like they were in 2018 and 2019.
I'm waiting with my list of flights I 'd like to see United try in spring/summer of 2022 even if only for one season. I know they all won't happened but I would like to see.
IAH-CDG, IAH-FCO, LAX-FRA, LAX-TLV, DEN-AMS, DEN-CDG, ORD-BCN, ORD-ATH, EWR-NCE, EWR-PMO, IAD-VIE, (crazy as this may sound make peace with Emirates) try EWR-DXB, and also bring back/resume SFO-CDG, SFO-AMS. Again I know all of this won't happen but it would be good to see United try some of the more logical
routes next summer.