Oliver Cowdery initially wrote “the season soon cometh” in 𝓟; then almost immediately he crossed out the soon and supralinearly inserted speedily. The correction shows no change in the level of ink flow, so probably 𝓞 (which is not extant here) read speedily. The text is about equally divided between “coming speedily” and “coming soon”, with 12 occurrences of the first and 10 of the second. In fact, later on in verse 71 there is an occurrence of soon (“against the time which will soon come”). We find similar variation in usage elsewhere in the text:
Thus there would have been no motivation in Jacob 5:71 for Oliver to have edited soon to speedily.
Summary: Maintain in Jacob 5:71 the corrected reading in 𝓟, “the season speedily cometh”.