What he means is that many other games out there do it the very same way. To pick a rather random example, as i play it: Elder Scrolls Online. For example this year in spring it got the Greymoor expansion. At the same time, the Elsweyr expansion was removed from the store and became part of the base game. A year earlier, when Elsweyr got released, the previous expansion (Summerset) was removed from the shop and became part of the base game.
You see a pattern? Also note the advantages for either side: players who did not buy the expansion also get it, just one year later. The developers on the other hand have have an easier way of maintaining the game, they merely have to look at "base game with Greymoor" vs "base game without it" and not "base game with Summerset but not Elsweyr but with Greymoor again" and so on.
I picked this example because i actively play this game. I know of a number of other games who went the same or at least a similar way, but as i don't play them and thus don't know them well enough, i stick to this one example.
For ED the advantage is even more logical: how to sell people an expansion where they can walk on a planets surface, if they can't even reach the planet yet? Including it into the base game was a logical move, basically required to even market the next expansion. The only surprise here is the date, i would've expected this to happen at some time next year.
The last part is the one i have my doubts at. The game relies way too much on the BGS, so i fear that converting it to be able to run offline actually is a good deal of work. And that's where my confidence ends: i don't believe that FD will still invest the time and money for a game which doesn't create revenue any more.
You are wrong. Not sure about which Elder Scrolls Online you are talking about, but when you get to the DLC store on the "www.elderscrollsonline.com" the "Elsweyr" expanison cost 3500 of their couns, the "Summerset" cost another 3500... On which basis you got impression that they were merged to the based game?