While there are some examples of it not working, people tend to go where the investment and jobs are. Companies will want to go where the interest is.
What investment is coming into Wales to create jobs and interest? There is no cap on the budget for crossrail or HS2 but it's been very easy to find reason why investment into Wales isn't financially worthwhile...except if it also benefits Bristol.
Wales can grow up but relying on Westminster, especially one acting as it has over past 10 years, isn't it....but that doesn't necessarily mean independence.