Right now, cow stem cells stimulated to reproduce.
Actual meat that was never connected to an animal grown in a lab?
The cost is fantastically prohibitive as it is, but then, that's the way a project like this starts. As far as I'm aware there haven't yet been obvious technological objections to growing more in-vitro meat.
Stipulating that this becomes a practical method of producing meat fit for general consumption, then, those who are vegetarian (or vegan) for primarily moral reasons connected to not wanting to unnecessarily harm animals might choose to eat this: after all, no animal is immediately harmed by its production.
They might not, however, since developing the technology did demand the killing of animals along the way (if nothing else so people would know that the final product looked and tasted and felt like animal-bred meat), and they might wish to avoid being the beneficiaries of harm for a benefit they regard as trivial.
And those who are vegetarian for other reasons might well find the difference unimportant.