Well they are thus far copying this model from Destiny 2. If they follow that, then the first season will be included in the expansion. If they try to milk another $5-$10 on top of the expansion cost, that would upset most.
But this is Ubisoft, so ya never know. I mean they are releasing a pay to play expansion just weeks after their obligations for Year 1 are completed when the game has been in shambles since launch.