Wow, I think it's too early to talk about 5090, it will be out after more than a year from now, everything can change until then.
I doubt the mining market will change much,no coin,no actual coin looks like being able to be substituting the ETH profitability we had before ETH moved to PoS.The 5000 series sure will make these most used cards in mining cheaper in price but I doubt it will make them less relevant as the difference between 4090 and 5090 does not seem to be at a super high level of performance,most gamers still will be happy with 3090 as the best card for gaming,pretty much that together with 3090 ti can play every game in maxed setting even for the most demanding gamer,so 5090 although is distant in time from now,most likely won't change a lot of things.
well, except for VEGA 56, because I rarely see them on sale. 
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