Yep. Even if it's only an eight core part hitting 5.0 GHz with increased IPC it will be really tempting. If it actually hits the leaked numbers it the 3700X will be four times faster than my overclocked 3570k at multithreading and actually have increased single thread performance!
Zen (1xxx parts) already has higher single threaded performance over your 3570k. It just can't clock as high, but doesn't really need to.
3.8GHz Zen ~ 4.5GHz Sandy ~ 4.3GHz Ivy (~+5% over Sandy)
Zen+ (2xxx parts) is +3% over Zen. Zen2 seems to be +10-15% on average over Zen+ according to geekbench save for workloads that benefit from the upgraded SIMD hardware (similar to Ivy -> Haswell) where it's even faster.
Factor in meltdown/spectre/L1TF/MDS mitigations... then for a Sandy/Ivy 5GHz capable golden sample, its ~1000MHz clock margin over 1xxx parts and ~800MHz margin over 2xxx parts has just been made irrelevant.
Sandy was legendary and Ivy was a nice incremental improvement, but they're well past retirement for anything high performance thanks to the vulnerabilities and its mitigations. Sorry.
Anyway, whatever upgrade you do, most of the improvement will come not from higher ST performance, but by having a ton more threads available. 4 threads in 2019 can be painful.