It really depends. How much did you pay for your 13 Pro Max? How much can you sell it for? Do you have Apple Care on it?
Personally I would wait for the 15. It will have a couple pretty big upgrades like USB-C support-finally! It will also have a better processor with the a17 most likely being on 3nm. Just those two features I would want to wait for if I plan to keep the phone for a long time. It will age better.
Honestly the 13 Pro Max is one of the better iPhones made. It was the first iPhone with an adaptive Pro Motion display, better cameras, great battery life and double the base storage. Unless you had a 11 or 12 I don't think there are too many features you are missing in the 14 Pro. Sure it has a hole punch pill shaped cut out(copied from Android) and better cameras and a slightly faster processor but that is about it. Dynamic Island is kind of gimmicky to me.
Sure you have a large phone but is the Pro at 6.1" that much smaller or lighter? Still has stainless steel frame. Also there are rumors the 15 will use titanium. I kind of doubt it but if it were true it would be much lighter and stronger but more of a scratch magnet as titanium is a softer surface metal. So if light and Pro are a thing I would wait and see what pans out.
I have been tempted for the 14 Pro Max but trade in value or selling it second hand I would still pay more for not much in return. I really like the deep purple color but that is not enough of a reason to fork over $400 for it in my personal opinion. Plus I have Apple care until the end of next year which is right around the next release. If I sell the 13 Pro Max in November next year or September it will still have Apple Care for a couple more months which means if I sell second hand I can get a bit more or if a buyer has an issue they can take it to Apple. So it makes no sense for me to upgrade now. I think you may be in a similar position.
Only you can say whether it is worth it and if you want to spend the money.
I am also very curious about the new Pixel phones. I use Android and iOS and in 7 days the Pixel 7 will cost $499 and it has a 6.3" screen 90hz refresh rate, AOD, good cameras, call screening, etc. I have an S22 plus and with trade in Google would be paying me money so it is very tempting but my iPhone 13 Pro Max is not going anywhere!! Lol