Should the chart be no longer available on Wikipedia, the market will resolve using another neutral source that tracks average long-term warming compared to pre-industrial temperatures.

Could you say more about which? It seems fairly likely that whatever graph Wikipedia replaces that graph with won't have a 20 year average, and the exact choice of source is going to matter a lot to the individual resolution year.

Following a simple linear extrapolation from the linked graph:

y_T = y_1 + (T - T_1) / ((T_1 - T_0) / (y_1 - y_0))

= 2024 + (1.5 - 1.25) / ((1.25 - 0.35) / (2024 - 1976))

= ~2037
with a margin of error of a few years to account for unexpected acceleration/deceleration