Great discussion. I have been active in licensing discussions in Austin TX for a number of years, and also part of a group of CAs that have been discussing state wide licensing. While many of us would really like to see the better consumer protection and differentiation between "good" and "bad" companies that you think licensing might help bring about, we have come to the conclusion that the success of licensing really pivots on execution and enforcement by the government agency. Our city forestry department has said privately they want no part of enforcing licensing, as they can't even fully enforce things they already oversee, like tree preservation.
And so we really don't see it happening in Austin. As for Texas as a whole, well, I think most of you know what it's like here. The chance of any consumer or environmental protection happening here, especially if it impedes anyone's chance to make a buck, is about ZERO.
Hats off to city of San Antonio for putting a licensing requirement in place. However, many arborists in the Austin area have also seen locally based tree care restrictions back fire. Two small (wealthy) towns adjacent to Austin passed rules that were not science-based, theoretically to prevent the spread of disease, and the result has been that the best arborists in our area prefer not to work in those towns. Point being, if licensing is to be done, competent arborists MUST be involved, or the result will be sh*t.