No, they will work together. The next one will build on Entrenchment.
I thought that the way mini xpacks were designed means that a player could f.ex. have the diplomacy pack, but not entrenchment, thus not having starbases and other defensive enhancements. or a player could get entrenchment, but not the diplomacy one. and the same for the 3rd pack.
'build on ...' can mean many things.
is there a requirement to have one for the other to work? I'd doubt that. one point was to give customisability iirc.
does the second pack automatically include all features of the first and would the third include those of one and two? also doubtful, because earlier customers would feel pissed, if each pack's price remains ~ 10$ (not that it's not a fair price. just, getting it for more or less free with the next pack is ... new).
does each pack give the features promoted and ignore the other packs? basically as in the first paragraph? well, what does build on mean then? technical? doubtful, since with entrenchment the engines were apparently different enough for some changes to be ported causing quite some effort.
so, I am back wondering what was meant here.
