Commercial? In the 70's, 80's maybe, nowdays just no LOL. Their songs are still longer than your average radio friendly song, even if they are short for DT standards(and not so much f you look at their entire catalog). Their song length and accessibility is on the same level as I&W, Awake, FII and Octavarium, so if "they are going commercial", they have been for really long time, and I don't think it's a bad thing as long as they don't compromise their music only to fulfil that purpose. And actually there are several ways to be commercial, and not all of them mean the same depending on the band you're talking about but that's a different topic altogether.
The feeling thing again is on the listener connection to the player, so it's entirely subjective. A discussion that goes nowhere.
Finally, there isn't a correlation between song length and progressiveness or quality, while some of the 10-15 minute songs are my favourites, other are just a huge miss, and so are some shorter tracks. Surrounded, to give a fan favourite example, is short but with a lot of changes, so is Behind The Veil or Surrender To Reason on the latest album. Whether you like it or not it's completely subjective, but I don't see a difference in the way all these songs where constructed, they are still 100% Dream Theater, with all that implies.