Some observations I've made so far:
We are really a small player in IAH, with around 20 lines/seat/month. Mesa has around 180 lines/seat/month (info from forum) and 60 aircraft in IAH (according to website). ExpressJet has a significant presence too, and with their first 5 Ejets going to IAH, the flying is going to have to come at the expense of another Express carrier, due to United scope limits. Also, all of these operators in IAH are staying afloat because of United. Republic has done just a little bit of Delta and American flying, but not consistently.
Mesa has Ejet contracts that start to expire mid 2019. United can choose whether or not to extend those. Also from the Mesa forum, there is talk that some of their airplanes (which are mostly leased from UA) will go to ORD. This could happen with ExpressJet too. If so, it must mean United doesn't care that we already have an ORD base, with many (senior) captains eager to get based there. If ORD shrinks even more at Republic where will those captains go to escape reserve?
At least now we are starting to see some evidence that the company is working on growing IAH. FO and CA vacancies have been steady, and the May 2019 award has more CA vacancies than usual. If the FLICA denied awards report is a valid measure of pilots looking for captain in IAH, then next month we'll see the most junior IAH captain improve by 1 year, putting it on par with the rest of the more senior captain bases.