Universal had a bad 2009 because a lot of people postponed their vacation until Potter opened in 2010. Ever since then they haven't started the PR push for new attractions until they are in the window that people are booking vacations for the period when it opens. So for the Potter Coaster, I would expect marketing to crank up after the Holidays this year. Until then we will get HHN and Holiday marketing. After the first of the year it will be Mardi Gras and Potter.
Disney is feeling this effect now with SW:GE. And it will be even worse next Summer.
And as far as, "Why advertise at all?" Universal has found that advertising something already open or about to open is productive. Advertising something that opens next year makes people wait until next year.
I think both companies have something to be learned, and there is a much happier middle ground. However the middle ground is further away from Universal.
Universal has been in the model of annual attractions, if you have something big every year, you don't need to worry about people postponing. Unfortunately they remain hyper focused on an experience in 2009, when they were a completely different resort and company. If the flow is steady, the guests will be steady and your marketing can be steady.
However, there are also different forms of marketing, the actual global marketing push and the marketing to your fans push. Disney overdoes both. But Disney is infinitely better at the second even if they milk their fans aggressively. Universal severely underplays to their fanbase to the point of near discontent. They don't need to announce on Good Morning America their 2023 projects, but they could certainly let fans know
something will actually happen in 2020/21. Let alone more than two words about 2019. Somewhere there is a compromise.
Universal has a very bright slate, but they almost don't seem to want anyone to be aware of it and that is starting to affect perception. Disney has barely even opened anything yet... but they've been strutting around on the back of their future and that has instead sowed confidence (?overconfidence) into their consumer.
My personal perception is that they don't actually seem to be able to make decisions recently. They are overanalyzing and getting cold fit with everything they do.
