Your 2070 will be able to handle some heavy gaming loads for the next two years. So if will satisfy, seemingly, everything you needed and wanted.
If you wanted the best possible performance for the best possible price, you could have gotten an RTX 3070 for the same price as a brand new RTX 2070. But you didn't want to pay that price, so you got it at a discount. You ultimately paid less for a 2070 than you would have if you paid for a 3070, and it will most likely be just as useful as if you had bought a brand new 2070.
So all in all, if I was you, if you had done it, I'd regret having bought a brand new 2070, when the same-priced 3070 would be around 50% better. Since you didn't buy brand new, I wouldn't feel as bad.
Although, I would not have bought a used RTX 2070 for more than 50% of its new price, myself. I realize that there may not be one at that price, but I just would never do that for used tech myself.
All things considered, I don't think you have too much to regret, especially because you wanted the instant gratification, and this was probably the only way to get that. And it sounds like you were willing to trade that for some possible regret later. It's a trade off. But your 2070 will not be any less effective now after the 3070 is released on October 29th.