Offline solo mode was one of the reasons why I joined the beta. If this is really canceled I'll probably ask for a refund. When I buy something I want to make use of it when and where I want, without Internet connection problems, server issues, and I want to be sure that I can keep using it even if the software house decides to shut down everything.
You're right in saying that, but you agreed with the terms and conditions of the store as soon as you hit 'check out' there. As soon as you paid for your purchase, it was made available to you and from that point forward, you'll have to live with it.
There are outside means to get Frontier to refund you, but that varies from country to country and it will take a lot of pro-activity from your end and you have to ask yourself if you want to go through all that trouble. I fully understand if you do that for the principle of it, though.
I wish that Frontier had stated that Off-line was being looked at with a very slim chance of making into the final release; I would have waited for the finished product then. But yeah, I'm over it. I only regret that I won't get as much usability out of the game as I originally thought that I would. Right now I'm more worried over what else is getting dropped in return for five extra ships.