Stick to your Note 10+, no need to upgrade now, it will receive upto Android 12, so you can use that upto that time easy, then after that, you can consider Note 21 series.
Note 10+ will not get android 12 as it was released on Android 9 Pie (One UI 1.5) .. And Recently it got Android 11 (One UI 3.0) .. Maximum it would get One UI 3.1 or One UI 3.5
I am also using Note 10+ but I don't think either of them is a huge lead in front of Note 10+ except for 120 HZ And More Zoom but you loose Dedicated SPen and 45 Watt Charging.. I think Note 10+ will outclass or atleast equal Both of them quite easily and most importantly Your saving atleast 55-60K In terms of exchange and 1,06,000 if buying a new one 😉