I personally doubt it, but that is obviously just a matter of opinion since there is no official way to determine whether it's a step towards a more general legalization.
In my opinion, it is not a major step because the idea of medical marijuana seems so much different to people like me who disapprove of the use of marijuana in general. It seems to me that using a substance for medical purposes is much different from using it for fun.
So I can see a lot of people like me being okay with the idea of allowing it when prescribed by a doctor but not with the idea of just letting anyone use it because they feel like it.
So I don't think support for the one implies support for the other.