It looks like you could reasonably expect a resale value of around $200.00 for your RTX 2070 S on ebay. That's not great, but if you look at it like a discount toward a 3080, it is not bad. You'll probably get to keep about $170.00 after fees, so that is what I'll use for the math. You are going to apply that to a used 3080, 10 or 12 GB variant doesn't matter, just price. The best 'buy it now' I see on ebay is $520.00. So right now you could reasonably purchase a 3080 and sell your 2070 S and come out to $350 out of pocket. GeForce Now is going to cost your $240.00 per year and you have nothing to sell at the end of that. Let's say you hold on to your 3080 for 2 years, should be fine as it will still be in the ballpark of a 4070 when it is released since the 4070 ti is only about 20% faster, and then you sell it to upgrade to some 50 series card. In fact, the 3080 might still be significantly better than the 4070 is the rumored 5888 cuda-cores is accurate, that's a big drop from the 4070 Ti. So, you'll probably be able to recoup $150.00 or so even in two years minimum. So, two years of Geforce now $480.00, buying a used 3080 and selling your 2070 S and $350 out of pocket with the potential of $150.00 credit toward next purchase in 2 years... costs to upgrade for two years $200.00. Get the 3080.