Well, it may be that your Packman mirror is outdated, there has been a kernel update yesterday (and broadcom-wl has been rebuilt 23hrs ago)…
In that case, booting the previous kernel may help.
Of course it might also be that broadcom-wl is broken and would need a patch to work with the latest kernel.
Just to be sure: broadcom-wl is not enough, you need to install a broadcom-wl-kmp package that matches your kernel.