According to this article at SciFi.com it looks like Highlander 5 might actually get produced. Given the lackluster acting and script of the last film I am doubtful that Adrian Paul can carry the franchise forward by himself. The amusing thing will be to see what bullshit thing the writers pull out of their ass for this installment. Considering the prior films they have their work cut out for them.

Highlander 2: the immortals are actually aliens from the planet Zeist who are in political exile. They try to restore the ozone layer in a lame post-modern future. At least Virgina Madsen was in it

Highlander 3: forget all that alien stuff. Although all the immortals fought to the death in the 1st film we forgot about a few of them who happened to be trapped in a cave. Ops! They happen to break out and hilarity ensues.

Highlander 4: this time around lets try to tie it in to the spin off TV series. Lets kill the main character off for no good reason and then sidestep the obvious plot holes for the next hour of the movie. Look there are ninja guys on motorcycles. WTF?

It will be interesting to see how Davis & Panzer retread their cashcow for a fifth installment.