I have no experience with the last 2 companies you mentioned. Do they have the kind of eFPGA IP I've seen sometimes or do they only make CPU or fixed logic designs? The FPGA in the rfsoc has a lot of logic and DSP resources. It'd be a shame to give that up.
They do deliver the RF part, the customer design the DSP themselves, often by just writing the RTL but letting a 3rd party ASIC design services company to do the physical design. eFPGAs aren't popular, but for a good reason. One can add as much as programmability to a custom designed ASIC as possible, but specific to the application. It's extremely rare that one needs their own ASIC with general purpose logic. If you know your use case good, you don't need that.
Custom designed DSP almost always outperforms FPGAs because you can get the most out of the process technology. Also, FPGAs are often in 2-3 generation old process nodes. It is just way more expensive, but for these customers the performance edge often outperforms the price. High frequency trading companies cone to mind. They have transitioned from FPGAs to ASICs wherever it makes sense.
