It will certainly be interesting to see how this develops in the coming months and years.
My take on it?
Echoing a few others here and elsewhere, I believe that the "LIVE" elements will simply involve the ability to get addons (free or pay) through MS's marketplace system, and not much else. While MS did bin the ACES team, I find it hard to believe that they would revert FS....oh wait...I guess it's just "F" now

to an "arcade game".
If anything, it could result in what is basically a bare bones FSX starting platform, and the LIVE elements come into play with
anything that you want to add. While this may mean things such as "want something besides the included Cessna? ...pay us money" I believe that in the long run...the exposure that addon developers receive from this, including the free and payware developers here, will outweigh any extra "certification hoops" that one must deal with.
Basically, I'm imaging FSX with a completely different GUI when not in the flying environment. Of course, everything is going to be speculation right now, so we'll all just have to remember to "chill out" and wait until we receive more info.