Well, this is an interesting topic, albeit, it's coming about 2-3 years late.
As I have put forth in many threads on many different newsgroups, there is no stopping the ProTools juggernaut. It is and will be the standard format for at least the forseeable future. There is not a single company on the entire planet which could pose any sort of serious threat.
That surely doesn't mean that there are not many other, very worthy products...we've all discussed many of them through various threads. Logic, Nuendo, Radar, etc., etc. But even though these formats might have their supporters and users, if you're asking which company has or had the best opportunity to unseat Digi, the answer is ever so clearly "No such company exists". Digi losing the market will not happen for a long, long time, simply because formats which become so firmly entrenched do not come along very often. Over the last, say, 30 years, did any format actually unseat 2" tape to become THE most widely used format? Probably not...sure there was ADAT and DA88 and Sony 3348 and Mitsu digital, but did any of these actually displace 2" and the most popular format?
Not that we should be unhappy about it totally. After all, ProTools is a great product, all things considered. And, it's only going to improve from here. Mixing within ProTools will become more and more popular, and as more and more engineers become ProTools gurus, our methodry will improve, thus creating better sounding records using the sytem.
The only downside to all of this is that the format is owned by one company. I do consider that to be a considerable downside, but, it is what it is. If you're wondering which company could mount an attack of merit, of course, there is none and won't be for a long, long time...it could be game over in this area of the audio industry until something altogether new comes along.