If you’re starting to get into 4-series projects but you don’t have actual hardware to test with you can load SIMPL programs targeted for 4-series processors to a 3-series. I’d heard the reverse was true: a 3-series programs should run unmodified on a 4-series. But it looks like for testing purposes, you can also run 4-series SIMPL programs on a 3-series.
Of course, your program would need to be written such that it runs on a 3-series and a 4-series. This is different from the 2-series to 3-series transition where the architectures must have been wildly different.