My take (as a vegan):

• Most lab grown meat still has animal product input so it's not vegan
• In the event that they replace that part of the production, there's still a good chance it gets tested on animals to get GRAS (generally recognized as safe) certification from the FDA. I don't eat e.g. Impossible or Just, both of which tested their food on animals to get the certification.
• If there existed a way of synthesizing meat that didn't have animal products as input and was never tested on animals, I'd be very excited about it from the perspective of getting omnis to stop killing animals for their flesh or secretions. I probably wouldn't eat it because of the ick factor, plus health reasons, but I think it would be vegan.

I also don't think that waiting for lab grown meat before going vegan is a morally defensible position in general.