Hi,
Logic doesn't use VST (and AFAIK, Cubase/Nuendo don't use AU, but I'm not sure about this one...).
in no way shape or form do i think it's accurate to proclaim that, today, Logic is the "accepted standard."
In my experience, the 'accepted standard' in high-end rental studios has been PT (TDM) for some years. After Apple started to give away Logic and all those plug-ins, sounds and extra apps for free, all these studios seem to have Logic installed as well (if only to be compatible with their clients).
What I've seen lately is that more and more high end users keep their PT rig but start to work natively in parallel with using TDM, normally with Logic.
not only does Logic not have the marketshare
Well.... marketshare and marketshare are two different things. In the Mac world, PT (the TDM version) represents a very small part of the total market, simply because of it's price (also because it currently is dramatically overpriced), and because all other systems cost only a fraction of a HD rig (which still is more or less priced according to the value of a PT HD rig anno last century).
If we're talking about total marketshare (all installed DAWs on Apple computers), Logic's marketshare is rather massive, for various reasons - one being that all Macs come with GarageBand (= Logic Extra Light) preinstalled.
or that Apple may ditch the product entirely.
No way... the only reason they IMO possibly would ditch Logic would be if they launched a new DAW, competing with Logic - just like Emagic ditched Notator for Logic. If they'll do that, I'm sure there will an upgrade path, and a certain level of backwards compatibility.
I've owned every Pro Tools rig from PT four voice up to (and including) PT HD, but being fluent in
Logic was a requirement for getting the last major projects I've worked on. Artists and composers know that they don't need PT HD to make and record good music anymore, and the LE version of Pro Tools is partially crippled, partially inefficient. After the release of Logic 8, Apple put a lot of effort into increasing performance (track/plug-in count), both with the two sub-releases of Logic and the sub-releases of Leopard.
In a way it's kind of unfair... but one can't really beat a company that both owns the hardware, the OS and the DAW.