How likely is it that Twitter will succeed with Jack Dorsey at the helm of the company?

I think highly, highly likely.

For just one simple reason.  90% of what matters after you are at scale is the management team.

The best will want to work for Jack.  Heck, I almost want to work for Jack.

Maybe that will fade.  But I think right now, he can and will attract just amazing people to Twitter.

And all Twitter needs to do is a Little Better to really kill it.  Just monetize the base a little better.  Make the product a little less confusing.  A little more accessible.  To grow even faster than they already are.