I highly doubt it, Windows is known for its stellar backward compatibility. Code signing means a lot of older software, that is still in use, would not be able to install or run. This is not going to happen (at least in the enterprise).
I have mad respect for Microsoft engineers for the compatibility work that they've done over the past decades. It is indeed superb that you can take even today an old Win32 executable and run it and it'll just work.
But I expect the new leadership will not put much value on this. I imagine it'd play out that first to "to enhance the security and improve the UX" they'll start a shoving a bunch of nagging dialogs in the users face "this app is not safe" etc.
Then they'll add a flag to enable "unsafe mode" where the user can run unverified / unsigned code.
Then finally they'll just nuke the flag.
After all requiring that the ecosystem with the most "important" apps such as their own office suite, slack, adobe etc. grind out new versions with digital signing is not out of alignment with these companies incentives and development cycles either.
In fact I would not find it surprising if these companies would actually be approached by Microsoft to participate in any such scheme and get offered some kind of "discount" or reward (whether it's app store discount or whatever else) and these companies would only see it strengthening their own moats against any possible competition.
And I'm talking about the consumer use case, not the corporate.
You don't know how many ad-hoc legacy apps based on Java/C# are out there. Zillions. If you want to give GNU/Linux a huge chunk of share (Java and C# code from early 00's/2010 will run everywhere), MS would face a huge disaster and billions of loses.
