> I wonder what will be the next category of open source to pull ahead?

KiCad, for PCB design. They have been making massive improvements over the last few years, and with proprietary solutions shutting down (Eagle) or being unaffordable (Altium) Kicad is now by far the best option for both hobbyists and small companies.

With the release of KiCad 5 in 2018 it went from being "a pain to use to, but technically sufficient" to being a genuine option for less-demanding professionals. Since then they've been absolutely killing it, with major releases happening once a year and bringing enough quality-of-life improvements that it is actually hard to keep track of all of them.

From the type of new features it is very obvious that a lot of professional users are now showing interest in the application, and as we've seen with Blender a trickle of professional adoption can quickly turn into a flood which takes over the entire market.

KiCad still has a long way to go when it comes to complex high-speed boards (nobody in their right mind would use it to design an EPYC motherboard, for example), but it is absolutely going to steamroll the competition when it comes to the cookie-cutter 2/4/6 layer PCBs in all the everyday consumer products.