Is the M4 Pro processor enough for 4k editing?

Any fairly recent can do that. The M4 Pro is awesome and can do that, easily.

FWIW, I have edited 4K material in FCP using an Intel Mac.

My daughter even worked in 4K material on a 10 year old MacBook Pro - and still does today, albeit on small projects.

An M4 Pro is more than an order of magnitude faster than that. It is a beast of a machine. There is no need to splurge for the Max.

You can also do what you want with a plain M4, although of course the M4 Pro will be more powerful.

I recently got an M4 Pro MBP and it is a marvel. I am planning on keeping it for a long time.

Note that the M4 Pro is even faster in some tasks than the M3 Max - and beats the M1 Max that I have tested at just about anything.

Maybe your demands were different and heavier than mine, but I have edited some 4K material with a 2019 MBP, and before that with a 2014 model; my daughter still uses a 2013 model, and that can edit (albeit slowly) 4K material.

Maybe there are other limiting factors, like memory and, especially, the drives. I always edit on SSD, either internal or external. If you were using a slow rotating hard drive, that was probably the weakest link.

Or maybe you had installed software that hurts video applications - any antivirus, "cleaners" or... chrome and its background processes can and do hurt FCP performance or cause crashes, especially in more demanding setups.

If you want us to have a look, you can post an Etrecheck report from your current machine. Odds are that what you have is already enough, or you can at least make do with it until you get the new mac.