This is a fantastic innovation in the making. As long as the "lab-grown meat", doesn't have any negative side effects on health and environment, it will be good for the "carnivores" to switch over to it.
We have already caused a lot of pain and harm to "sentient" animals. Its our evil karma that has been piling up as sin and comes back to us in form of various problems and stress. If it is not right to kill someone just because we want to rob that person and get rich, then neither it is correct to get "proteins" by causing such immense pain to "sentient" animals.
Hope, this makes us more compassionate.