The successor of the 3S-GTE (2.0T, 400+PS, 500+N.m) is more or less confirmed to happen. It doesn't make sense to only use that engine for the Celica. If they are aiming for volume and thus profitability the natural choice is a GR RAV4.
A GR version of the LC250 with 3.4T iForce Max could happen given that they still have a lot of room in GVM.
My prediction of the most likely GR cars to be release in the next few years:
Starlet (1.4T 180PS FWD)
MR2 (1.6T 320PS RWD)
Celica (2.0T 400PS AWD)
Supra Mk.VI (3.0T 420PS RWD)
Hilux (3.3T diesel 320PS 4WD)
Prado (3.4T hybrid 470PS 4WD)
RAV4 (2.0T 400PS AWD)
This is quite sad. GR has been incredibly successful. Why wouldn't they get more development dollars?
Because they wasted quite a bit of budget on cancelled programs. The Hypersport was cancelled after the prototype was destroyed in a fire. The mid-engine GR Yaris was delayed by supply chain issues and rebooted as a limited production MR2. The MR kei-car collaboration with Suzuki and Daihatsu didn't materialize and will likely be restarted as the S-FR program. The Supra BEV was a distraction that probably gets pushed back until solid state batteries are ready and rebranded as FT-Se. Not to mention the Lexus F side got zero product in the past 5 years. GS-F, cancelled. LC-F, cancelled. LS-F, cancelled. LF-1, cancelled. LFR, delayed. Some cancellations are deserved and some are not.
A lot of these probably wouldn't have happened if they didn't cave in to shareholder pressure and wasted a bunch of effort on impractically ambitious BEV projects. Especially the Lexus side that still hasn't publicly abandoned their 100% BEV plan.