Well, the 7800X3D is currently the most powerful CPU for gaming! (Unless you have a game that can utilise a lot of cores, which is rarely the case) It's definitely worth making the switch. Of course, your old 3070 will be a bottleneck in the system, but you say you'll fix that next year. So it's all good! Have a look at some good reviews of the 7800X3D, there are always gaming benchmarks in comparison with older CPUs. You'll see the differences very clearly.