The more I think about it, I think they really will give Ash Tyranitar, because if Gengar is to make up for Ash not getting Haunter, And if Riolu is to make up for him not getting one in DP then the one Pokemon Ash was robbed of was definitely Larvitar in Johto. He hatched its egg and bonded with it. So I do think they probably would make up for that by hopefully bringing back Larvitar as a Tyranitar.
I mean it would be interesting to see Larvitar itself come back, rebond with Ash, Ash catches it and Larvitar in excitement after immediately coming out evolves into Pupitar at the end of the episode, and then Ash later evolves it into Tyranitar, maybe even 5-10 episodes, with perhaps a happy Tyranitar or something.
But I'm fine with Larvitar being grown up, I just think it might be possible for Larvitar to come back, but I do think it would need to evolve into Pupitar after Ash catches it immediately, so we don't have to waste much time before it becomes a Tyranitar.