A better question will be, How much does the i7 9700F cost you? and How much does a new B550 mobo + Ryzen 5 3600 ?
Also what kind of RAM do you have, capacity, and speed?, Is it a 2x8 GB kit? or just 1 single stick?.
Intel 10th gen and Ryzen 3xxx like and need fast speed RAM to get those flashy numbers we see on reviews, so if you only have (for example) 2x8GB DDR 2400 kit, then you would probably be better off keeping your current mobo and swapping the cpu to that core i7. For Ryzen and newers games you wany at least 2x8GB DDR4 3200MHz memory kit.
As for Ryzen 4xxx series it seems the second week of october is when AMD will release the technical data, but theres no word yet on when will they be in the market. Coudl be the same day, a few days after it, or who knows. Seems to me AMD is doing really well with Zen 2 and is not in a rush to bring zen 3, after all intel does not have anything new to offer till next year (when I hope they will bring 11th gen with pcie 4.0 support).