If he plays his cards right, he is capable of 2:11:30 and a top 3 spot to make it to Tokyo. I think most would agree that if he puts in a solid road marathon specific training block, he can be in 2:11:30 shape.
The reason I think he will be top 3 is looking at Magda Boulet. Shes won western states once or twice I believe, and has had varying degrees of success with other ultras like UTMB (5th). She also ran under 32 on track for 10000m and had lots of success with the marathon making the womens team in 2008. While the situations are slightly different because men's and womens talent pools are different, Jim walms and her look pretty similar on the ultra scene on paper; some blow ups, but generally consistently placing in the top of the fields or winning ultras and both went to D1 college and had success.
The ultra community is definitely a smaller talent pool than the marathon, but Magda proves that not "any decent marathoner" can come in and dominate. She was second at the olympic trials and ended up 5th at UTMB so theres some heavy hitters in ultras. I think JW may be one of those talents in ultras that could really show up in the marathon if he committed 6 months out.