But it's the 'if' in your last sentence that worries me, do you think not leaving is now a possibility?
Honest answer.
It has been an 'if' since referendum day merely because the result is not legally binding but only politically binding.
There are practical reasons why it might not happen and they have always been there. That's not changed because of this ruling. I'm not sure that the chances of leaving or not leaving have changed as a result of the ruling either.
It a reflection of four things: the narrowness of the result, the demographic of who voted for the winning result, the very complex nature of leaving and the economics of leaving.
These are realities that are unavoidable. Part of it is about the political will to leave but part of it is also about our ability or capacity to leave. (By that, on our terms and not because of something the EU does or does not do). These are different things; so far we do have the political will, but we are yet to develop the capacity to (call it The Plan if you want to simplify it).
Until there is a firm plan which the public and parliament are party to, then yes, it is still definitely an 'if' about whether we leave.
How you go about Brexit was and still is about the need to build a consensus for both will and capacity. May's approach so far, has not been helpful to that in any way. Its just polarised opinion and raised other fears about what Brexit will bring and has actually alienated Europe even further.
This is why I say, I don't necessarily think the ruling today means that Brexit is less likely. Why? Because it might mean that the political direction now is forced to build that much needed consensus.
Realising this and working with Remainers is more likely to ensure Brexit will happen, though this might sound counter to what you think. Forcing the issue will only make people more afraid and get them digging their heels in.
Brexit has to be a compromise for all, not something imposed, for it to work and for it to be viable.
Leavers can not simply go "we won! lets brexit now!" because that's not the reality of the system. The system is like that for good reason, even if its damned frustrating for all of us at times (and is undeniably flawed and in much need of reform).