The 3090 RTX is also $1000 cheaper than the Titan, so there's that. It would be nice if there was a good way to express value per dollar. Perhaps in GLUE accuracy and training time.
So if you're someone who does their work mainly in FP32, you will see improved performance with the 3090. On the other hand, if you are an FP16 speed demon who needs to train GPT-3 over the weekend, stick with your Titans :)
But on 3090, I don't think the speedup will be 5x, it should be closer to like 2x. The 3090 has 35.6 TF/s at TF32 and the Titan RTX has 16.3 TF/s at FP32. Once again I think there is handicapping going on for 3090.