The answer depends on the situation.
If your installed .deb file has repository enabled or get enabled while installing, installed .deb packages will be updated. But, if your installed .deb file has no online repository, from which it can get updates, that package won't be updated. The reason is clear, the package manager doesn't know anyway to update the package, because it doesn't know any online repository providing this same package.
If you have synaptic package manager installed, You can see those packages who do not have any repository enabled, or installed with .deb files without enabling a repository. Open synaptic package manager, Click status section and see under Installed (local or obsolete) section.
Google-chrome and dropbox enable a repository while installing from .deb files, so you will get update for these packages.
Note: The same rule is true for packages which you installed via apt-get but later disabled the repository and no other repository provide those packages. In that case, you won't receive updates for these too.