They still haven't and probably won't answer what will remain available for non ttk owners. Even if that question hadn't been asked, it's their job to provide information as it relates to now when it comes to original content. Why? Because that original content is somehow supposed to link with the rest of the story. If non dlc cannot level to 40, then there would be no NF for them. It's stated that the Taken King strikes will be level 40, but what about other game ending strikes? Septiks, Archon Priest, Nexus...etc And if there at least 2 strikes coming with TTK, I'd hate it for players who haven't bought a single dlc. That means the rotation could be 4-6 dlc nightfalls in a row, depending on your game system. Yet again, we receive no answer. It kinda falls in line with our current health care system...you have to pass the bill in order to even get a look at what it contains. Or in this case, they want you to buy the dlc just for the possibility that your question may get answered.