Wow! That's a question. I'm very pessimistic about the future for British comics created and published in the U.K. However, imported comics seem to be selling reasonably well, particularly manga. Not sure about American imports as I don't have much connection with comic shops these days and the few newish comics I buy are not from Marvel DC and other mainstream publishers, but are digital editions of things like Bandette from Comixology. And Digital editions of Diabolik from Amazon.
I haven't read 2000AD in years and Beano and Dandy - before it's demise - were depressingly awful imo. But about 10 years or so ago my interest in old British comics was re-awakened and I started to accumulate and read (well, devour is a better word) pocket libraries, Eagle, Buddy, original superhero/MMM comics from the '50's etc. And as can be seen from the bidding on ebay, there seems to be a good market for that stuff.
As for the rest of the world, despite reports that sales of GN's in France and Belgium are declining, when I'm in shops there, they always seem busy and tills are ringing. Customers seem to be buying new GN's and old material. I did note that in Palma, the Norma shop has shrunk back to the original?/old location, offering nothing like the range of 2 or 3 years ago. But Gotham is or seems to be thriving.
Verona Fumetti - in Verona oddly enough - is still there and going strong with a huge range of new material and wonderful old, obscure, collectible back issues of all sorts of formats.
I recently managed to get to some shops in Brussels and, as in Verona, the choice was amazing. Same in the shops I have visited in parts of the Netherlands.
But I do believe the future will increasingly be one of digital editions. Sites such as Comixology and Izneo offer a huge range of comics and the guided view offers on Comixology are increasing. There are some free ones available for anyone who hasn't experienced them yet.
I have to admit to never having read Overkill and despite being hopelessly addicted to superhero/MMM comics, new versions of classic characters leave me cold, probably because they seem to me to be angst ridden and violent. But that could be me getting old.