I'm not a lawyer but have been involved in researching patents as part of my job. You are correct that there are lots of ways that patents can be extended, typically by demonstrating a new use or application for the device. Somewhere here on the forums a member with better patent experience than me was able to follow the string of patents and arrived at the latest active date, which happened last July. That's not to say that BM doesn't have action pending to extend their exclusive rights. Anything goes once things get into the hands of lawyers!
In terms of legit companies not offering an Axis lock, I think it makes sense that they aren't (yet). Given the cost to design, prototype and set up assembly for an entirely new knife with a new lock...I can't imagine companies like Spyderco or KAI spending resources until patents have definitely expired. Even then, there's no consensus that the Axis lock is the most desirable lock in the knife world, so many manufacturers may simply choose to not pursue it. I think the proof will be in the pudding over the next few years if legit companies begin to offer "Axis" lock models (not using that name, of course). BTW, I love this write up by Doug Ritter breaking down the benefits of the Axis lock...
http://www.dougritter.com/pop_up_axis_lock.htm
Its only the scum buckets like Ganzo that have no regard for law and potential litigation that are already geared up to offer a stolen design feature

Ganzo seems to epitomize what is worst in all cloners and counterfeiters; not only stealing patented components but outright copy of design. Yuck.