I don't think re-spin would right word for porting from Samsung's 8nm to TSMC's 7nm.If they are going to do a Titan then it should be on TSMC 7nm to really set it apart from the 3090 in terms of performance and efficiency, would probably need to be priced around 4K to make it worth Nvidia’s while.
But then redesign wouldn't be it either. So, something in-between.
I could imagine such a port taking largish team maybe 9 months to a year.
Question then is, what did Nvidia guess would be the market situation one year ago, or whenever they realised Samsung's 8nm was a lot worse than TSMC's 7nm?
Titan is far too small a market for the millions the port would cost, so unless they have other products which could use that die, I can't see this happening.