Recommendation from someone who was laid off: There is absolutely zero reason not to start looking now while you're gainfully employed. Even if you ultimately want to wait it out, applying to a few open positions a week will give you a sense of your response rate so you can set realistic expectations for how hard you'll have to hit the ground running to find something else. The other thing to consider is that the fact a place is hiring is a sign that HR hasn't written off that team, even if layoffs are on the horizon for parts of that company. You can also always ask the interviewer what their read on the company's solvency is, if it seems shaky to you.
If you wait to be laid off, remember that a lot of job applications will ask you for "reason for leaving" your previous jobs, and it's liable to come up in job interviews. Someone being laid off for budgetary reasons isn't a sign of a low quality candidate, but it isn't a gold star either, and a lot of hiring managers are inundated with resumes and quick to find reasons to throw one out.