Do you always upgrade to the newest generation of i3,i5,i7 when doing a pc build?

You have to figure out what is best for you. Right now the newest Intel desktop CPUs are 9th generation Core series like the 9700K. These CPUs have more cores than the previous generation so they are going to be smoother for streaming, but if all you do is play games you can buy an 8th generation CPU and save some money. My CPU is an Intel Core i5 8400, and I have no problems playing any games although I do not stream.