The Olympic Organizing Committee submitted a new proposal requesting exclusive use of Jingu Stadium from July 1 until about September 20 (the previous proposal was from May until November). They also plan to use the stadium a strictly s a resting area for VIPs. Jingu Stadium 2 (from January until November) and the Chichibunomiya Rugby Ground will instead act as a resting area for staff and as a storage facility.
The four organizations that use Jingu Stadium (NPB, Tokyo Big6, Tohto University, Tokyo High School) would like to support the committee as much as possible, but would still like to see the proposal shortened a little more.
The Olympic Organizing Committee will also probably submit proposals for use of other stadiums in the Kanto region, like Yokohama Stadium and QVC Marine Field, if baseball and softball make it into the 2020 Olympics.
The Tokyo High School Baseball Federation is thinking about asking the city to build a new stadium that seats between 20,000 and 30,000. Possible locations include Komazawa Park and Toneri Park.
[UPDATE @ 7:34pm]
Sanspo provided a breakdown of the number of games played at Jingu Stadium per month this year, between March and November.
Source: Sanspo 5/14/2016