TV Series-When all but the last season can be purchased

I've been wanting to buy this series for a long time now but I cannot buy the the last season. Does
anyone here know why that is or if it will change? The rep at VUDU didn't know why it was. Thank
you all for the input!

 

No picture. What is it?

 

The top picture shows the cost of season 1 & the bottom picture shows no pricing at all.