I do not know how the infrastructure is, but from their descriptions of "Logical Servers" that is a non-physical server used to help prevent the things you are talking about. MMO's are not easily converted to internet cloud servers, also what type of cloud servers your company uses may be completely different. To include cloud servers if they are not used the features being put to those cloud servers might actually be a very big endeavor, massive rerouting of functions etc. I can't say for sure what cloud servers your colleague was talking about for your set up but though it is a good idea, it is possible they can't do that. For instance when we got 6.0 dropped, it wiped any partial level because of their number crunch. There was a question asked could they save the progress, the answer was they could with a 3 week server down time for that to be done, so some things are very hard to implement when there is a product running live.
Now real quick adding a world server is not a hard thing to do because they just have to get the servers for the worlds connected properly the software installed properly and named so that the relevant entries can be placed into the Data Center's information blocks and the UI's can show what is necessary, this can be done with backend patches and a small content patch thus there would be a little bit of a down time, perhaps added in during normal maintenance.
Good ideas though I hope some day there would not be an issue of massive player loads and no server caps.I will also say that is a very, very astute question but with an answer like that given and the unknown setup SE has (to you) doesn't fully answer the question.