We need a topic that covers how to avoid any sneaky MS tricks to force 10 on folks.
I assume that you meant the Windows update that added a Windows 10 updater to existing Windows 7 and 8 installations.
In my opinion, Microsoft did that so when the time comes, users that want to go to Windows 10 will have an easy way to update. It is completely optional and not forced on anyone. Combined with the fact that Windows 10 is free for a year after official launch, this will make a lot of people wanting to switch to Windows 10.
Personally I will switch to Windows 10 once Emsisoft and Valve start supporting it. Windows 7 is good until 2020 - that's 5 more years - but eventually people will have to make the switch like they did with Windows XP.
The current Windows 10 builds are only Technical Preview, which means it is a long way from official release (we don't even know what the real name for Project Spartan is). So I would say your worries are a bit unfounded.
Just my two cents =)