To add further context, most "new civilisation spotlight" sections in the update notes tend to be around 200 words. Gran Colombia's is anomalous because of the big section on their unique Great People. However, the section on Gran Colombia's balance changes from the October 2020 patch was only 36 words. When it comes to civilisation balance changes, the update notes seem to tend towards being quite short, for example "Drop Hacienda to .5 Housing." One change, 5 words.
Individual unit introductions (like for unique units) tend to be 20-30 words, and we can expect 3 of those. New map introductions take 10-20 words each, and we will be getting 2 of those. So, of the 3,792 words in the upcoming update, unless there is some super secret big new stuff yet to be revealed, only about 100 or so words are used for new units and maps. One would assume that, if a new gameplay mode were coming, they would have advertised it in the preview from Tuesday as they did with the maps and units. Reasonably enough we can assume that the remaining roughly 3,700 words are being used largely for balance changes, in addition to UI, AI, modding, and miscellaneous changes, as well as bug and crash fixes.
In other words, previous updates suggest that there is a lot more that can be fit into that remaining space not covered by units and maps. As a test, I tried typing out the announced civilisation balance changes from the video, and reached a total of 400 words, so the official notes for those will probably be somewhat higher or lower but close enough. That leaves 3,300 words for the other changes, and consider that the changes in the video were mostly quite significant ones.
I hope this gives people a better sense of how large this update ought to be. I know some of you are worrying how much exactly will change, and whether or not certain civilisations will see any changes. From doing these calculations, I feel confident in dispelling the notion that this update will only contain extremely minor balance changes. Even if every single civilisation (including the ones from the video) received changes comparable to Gran Colombia in October, the changes would only come up to 1,800 words.