I can speak to the "stopped planning" issue. John Major's (not that one) "War Plan Red" from the Historian LVIII (1998), and many others including Edward Miller's important War Plan Orange points out that planning for these sorts of wars was still very much active from just before WWI into the interwar era (1908-1939). War Plan Orange involved Japan; Red involved Britain. (Black was Germany, Green was Mexico; a fuller list of colored war plans is on Wikipedia.) Updating War Plan Red continued until the outbreak of the Second World War, even though the Washington naval conference and agreement of 1921-22 and subsequent negotiation put it on a back burner and updating seems to have been a bit sporadic. I remember running across stories on its declassification from 1975 (1974 I think was the actual declassification) which reflected a certain annoyance from the Canadians, who were a target for invasion in this scenario.

So no, Hay-Pauncefot (1901) did not lead to the abandonment of military planning, or even the prospect of arms races between the US and UK. Although conflict became a less realistic or palatable concern among people generally (and writers like future-PM Winston Churchill and H. G. Wells were quite vocal in this regard), military contingency planning continued right up to the Second World War. These plans were however not revanchist, but the normal work of a general staff in preparing for all possible situations, however theoretical the prospect.