If the online support for the xbox 360 is turned off in a few years. Can I still log on xbox live accounts?
Probably yes. The Xbox 360 is still a much-used console and support for it will not be given up so quickly. Should he but the consequences are not predictable for us now. But sign up should go further. You just do not get support anymore.
Of course, if online support is discontinued in the distant future, you will no longer be able to sign up for your account online and play online.
Offline should still go.