"The IP cores are a solution for some system designs where an ASIC or a board full of FPGAs are deemed a reasonable system implementation...."

I think an IP Core is a solution for when you are designing an FPGA/ASIC anyway, and need a controller as part of that FPGA/ASIC project - why invent your own (and all the associated tools), when the 8051 is well known & supported already?!

But as a way to just obtain a controller to put onto a PCB - instead of buying one from Philips, Atmel, et al - No way!