Here is what happened and where we are now.
PRESENTATION TO THE HOUSE ARMED SERVICES COMMITTEE SUBCOMMITTEE ON TACTICAL AIR AND LAND FORCES, UNITED STATES HOUSE OF REPRESENTATIVES, HEARING DATE/TIME: May 2, 2019, 9:00 A.M.
Rather than quote every congressional discussion regarding the end of JSTARS recapitialization and the immediate "successor" here I will summarize:
The Air Force terminated the recapitialization effort (i.e. "Joint STARS replacement aircraft") in 2019 with the "plan" of ABMS being the replacement. E-8C and RQ-4 were supposed to be the "bridge" to the introduction of ABMS. Congress though was concerned that the Air Force was going with this plan as they had no actual GMTI component of the ABMS system of systems defined and were just using the (old) JSTARS requirements in places. ABMS has not yet fielded any hardware as of 2024 and yet both E-8C and RQ-4 are pretty much already gone.
So that went about like this:
View: https://www.youtube.com/watch?v=XC8qrH3Zwog
However....
Department of the Air Force Posture Statement Fiscal Year 2023, Department of the Air Force Presentation to the Committees and Subcommittees of the United States Senate and the House of Representatives, 2nd Session, 117th Congress, May 13, 2022
PRESENTATION TO THE HOUSE ARMED SERVICES COMMITTEE SUBCOMMITTEE ON TACTICAL AIR AND LAND FORCES, UNITED STATES HOUSE OF REPRESENTATIVES, HEARING DATE/TIME: March 29, 2023, 3:30 P.M.
DEPARTMENT OF THE AIR FORCE PRESENTATION TO THE HOUSE ARMED SERVICES COMMITTEE SUBCOMMITTEE ON STRATEGIC FORCES UNITED STATES HOUSE OF REPRESENTATIVES
FY25 Space Budget Hearing,Honorable Frank Calvelli, Assistant Secretary of the Air Force for Space Acquisition and Integration, May 1, 2024
Lamborn Opening Statement at Hearing on Fy25 Budget Request for DOD Space Programs, May 1, 2024
Testimony of Dr. Christopher J. Scolese, Director, National Reconnaissance Office, House Armed Services Committee, Subcommittee on Strategic Forces, Hearing on “Fiscal Year 2024 National Security Space Programs”, Wednesday April 26, 2023
(and dozens more like the above. USAF has been very vocal with Congress, which is all public record)
So the plan, at this point, is that Space Force and NRO will at some point in the future a space-based GMTI capability (as well as space-based "AEW" replacing E-3 / E-7) and that will be integrated with ABMS.