There have been a few threads about this earlier in the year, so I have collected some of the useful information.

Some other people have estimated the selling point for a used 4090 would be around $1500 USD. At current USD retail, the 4090 sells for $1819. This would be a loss of $319 USD. However, on current resale sites such as Ebay, a used 4090 is being as sold at $1740. That's a much smaller loss of $79.

Some leaks have suggested that the 5090 could see a Q4 release this year (likely December) with a selling point of 2000-2500 USD.

Assuming the selling point could drop for a used 4090 at any time, would you either;

A) spend $79-319 USD to have a 4090 for a year, and upgrade to a 5090 when it releases. Or;

B) just wait for the 5090.

Obviously everyone has a different system so the answers may vary. But let's try to keep our answers from the perspective of buying a PC for the first time.