The RTX 4090 Ti would have followed the same pattern that Nvidia had done with the RTX 3090 and the RTX 3090 Ti. However, Nvidia leaker @kopite7kimi has Ered that there will not be an RTX 4090 Ti, but Nvidia might introduce new RTX 4070 and RTX 4060-class cards based on AD103 and AD106 refreshes instead.

The best reason is that there is no competition to the RTX 4090 from AMD.  Nvidia was thinking of a contingency in the form of a GH202 Hopper in case AMD pushed RDNA 3, but AMD seemed content sitting on its hands.