My experience is that starting with a 7, 8 or 9 speed hub you can usually put a 10 speed cassette on it. Sometimes, especially if you are starting with a 7 speed freewheel, you will need to use a spacer. This is because the sprockets are all significantly more narrow and you need to "extend" the cassette just past the end of the freewheel so that the lockring will properly engage.
I've not done a conversion to an 11-speed cassette but my guess would be that it would work the same way.
So, you really have two options:
1f you really want to convert, I would start with just buying the cassette and seeing if it will work with or without a spacer. If not, then you can buy a new hub or wheel. Realize that if you convert you are also going to be buying at least new shifters, and possibly derraileurs as well. You are getting into the realm of my favorite saying: "A new bike fixes everything."
Every shop I have worked with, and the three places I order from online all have multiple 9-speed cassette options. Staying 9 speed will save you a bunch of money and give you years of commuting work. If you are worried about the future, buy two and throw one in your parts bin or toolbox.
Note: The question is tagged Shimano, and for Shimano the compatibility over the years is very high. If someone is trying to do the same thing with a Campagnolo hub I would say the odds of being able to convert are much lower. Campy rolled out several different 7, 8 and 9 speed standards over the years