When I left South Africa almost a decade ago for Dubai I travelled with one suitcase and a hockey stick bag.  At 21 I did not have many belongings and those that did not fit could be left at my parents’ house.
A year later I moved to London. I shipped a 45kg box ahead of me and somehow I still travelled with a large suitcase, a backpack and the hockey stick bag. 
Upon leaving London for Stockholm 3 months ago I did some shedding. The charity shop across the road from my flat thought Christmas had come early. At least 5 trips, countless boxes and bags later I thought I had cut the clutter.  I moved to Stockholm with a 125ltr suitcase, 2x 75ltr duffel bags, a snowboard bag, a triple tennis racket bag, my Dakine Mission Photo and my trusty travelzone expander.
I am leaving Stockholm in two months to travel destinations unknown for an undefined period.  I am going to have to be ruthless with my culling, but given the right bag I have no doubt that I can do it.  The question is, what is the right bag? There are so many choices:
What size? I am thinking around 75-80ltrs.
What style?  A backpack? Even then there are so many options.
What price? Is a £300 backpack really that much better than a £120 one?
To wheel or not? I’m thinking that is just extra weight.  
How do you ensure it is secure? Lockable zips?  It will contain all my belongs after all. 
Keeping in mind I will be taking my Dakine Mission Photo with me, which will serve as cabin luggage and daypack. I ask all those out there who have embarked on similar journeys and packed their lives into a single bag, what would you suggest?

Dakine Mission Photo will act as cabin luggage and daypack.

So far I have seen two options that may fit the bill. 

Caribee Grand Air 80 Travel Pack