Manufacturing them is unnecessary. The technology behind them, while capable, has reached its limits and there isn't much scope for improvement,and there is no point in setting up production line to manufacture them again.
What should be done however, is retrofitting all the existing WAP4 locomotives, or a subset of them that still have a lot of codal life left, with latest features like Microprocessor control, Head-on Generation, disc brakes, TPWS etc. Most of the WAP4's still have more than 20 years of operational life left. While the traction cannot be improved much, at least their operational capabilities should be enhanced to support better signalling and advanced rolling stock.