Will these seasons ever come out on DVD?

I'm getting so mad! I have 1-3 and love them. I personally think they should package 4 and 5 together. I don't care for season four as much, because Shelly Hack was so stiff, but Tanya Robers in season 5 is gorgeous! I would really love to complete my collection - does anybody have a clue as to what is taking so long? There are many fans waiting for these DVDs...