I should introduce you to my collection of 7. 8. 9, 10, 11 and 12 cog rear wheels.....since I started in 90, we have the following campagnolo releases (friends don't let friends ride fishing gear)
1991 8 speed
1997 9 speed
2000 10 speed
2008 11 speed
2018 12 speed.
In the process, we changed wheel dish, axle length, spacer size, chain width and derailleur throw. you might be able to increase one cog, in some wheels but not all. You almost always need to replace your shifter and derailleur. My TT bike was made for 8 speed, won't even fit a 10 speed wheel, which is ok because I only ran 3-5 cogs