Is upgrading to Windows 8 necessary?

I have windows 7 OS installed in my laptop and it seems to be working fine. All my friends have upgraded to awindows 8 but it has been just an year since I bought my laptop so I don’t want to spend again on getting a new upgrade. But as it seems like Microsoft is announcing new Windows versions every other day, how long will there be support available for Windows 7? When is the next version of Windows coming out? Is it really necessary to upgrade to Windows 8? What are some disadvantages I have to endure if I don’t?
